diff --git a/appveyor.yml b/appveyor.yml
index 855f34f..d911de9 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,7 +1,18 @@
-image: Visual Studio 2017
+
+image: Visual Studio 2019
+
+init:
+  - git config --global core.autocrlf true
+
+environment:
+  matrix:
+  - solution: Semester4/BracketsChecker/BracketsChecker.sln
 
 before_build:
-    - nuget restore semester2/6.1/HW6T2.sln
+  - nuget restore %solution%
 
 build:
-    project: semester2/2.3/2.3.sln
+  project: $(solution)
+
+test_script:
+  - dotnet test %solution%
diff --git a/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckTests.fsproj b/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckTests.fsproj
new file mode 100644
index 0000000..8333a77
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckTests.fsproj
@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+
+        <IsPackable>false</IsPackable>
+        <GenerateProgramFile>false</GenerateProgramFile>
+        <RootNamespace>TestProject1</RootNamespace>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="FsUnit" Version="4.0.1" />
+        <PackageReference Include="nunit" Version="3.12.0" />
+        <PackageReference Include="NUnit3TestAdapter" Version="3.15.1" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.4.0" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <Compile Include="BracketsCheckerTests.fs" />
+        <Compile Include="Program.fs" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\BracketsChecker\BracketsChecker.fsproj" />
+    </ItemGroup>
+
+</Project>
diff --git a/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckerTests.fs b/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckerTests.fs
new file mode 100644
index 0000000..1474b3d
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsCheckTests/BracketsCheckerTests.fs
@@ -0,0 +1,33 @@
+module TestProject1
+
+
+open NUnit.Framework
+open FsUnit
+open BracketsChecker
+
+let cases = 
+    [
+        "()", true
+        "[]", true
+        "{}", true
+        "", true
+        "1", true
+        ")(", false
+        "(]", false
+        "([{[]}])", true
+        "[])", false
+        "[[]]", true
+        "[1]", true
+        "([)]", false
+        "(123)", true
+        "]", false
+        "(", false
+        "(1)", true
+        "[453]", true
+        "[23}", false
+    ] |> List.map (fun (string, result) -> TestCaseData(string, result))
+
+[<Test>]
+[<TestCaseSource("cases")>]
+let bracketsTest str res =
+    bracketsChecker str |> should equal res
\ No newline at end of file
diff --git a/semester4/BracketsChecker/BracketsCheckTests/Program.fs b/semester4/BracketsChecker/BracketsCheckTests/Program.fs
new file mode 100644
index 0000000..0695f84
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsCheckTests/Program.fs
@@ -0,0 +1 @@
+module Program = let [<EntryPoint>] main _ = 0
diff --git a/semester4/BracketsChecker/BracketsChecker.sln b/semester4/BracketsChecker/BracketsChecker.sln
new file mode 100644
index 0000000..a83a304
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsChecker.sln
@@ -0,0 +1,22 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "BracketsChecker", "BracketsChecker\BracketsChecker.fsproj", "{8751A404-2E55-4DBA-AC3E-6C90466F861F}"
+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "BracketsCheckTests", "BracketsCheckTests\BracketsCheckTests.fsproj", "{779136A1-1CC6-402A-A881-99A8E4337227}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{8751A404-2E55-4DBA-AC3E-6C90466F861F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{8751A404-2E55-4DBA-AC3E-6C90466F861F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{8751A404-2E55-4DBA-AC3E-6C90466F861F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{8751A404-2E55-4DBA-AC3E-6C90466F861F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{779136A1-1CC6-402A-A881-99A8E4337227}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{779136A1-1CC6-402A-A881-99A8E4337227}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{779136A1-1CC6-402A-A881-99A8E4337227}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{779136A1-1CC6-402A-A881-99A8E4337227}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal
diff --git a/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fs b/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fs
new file mode 100644
index 0000000..3b1b0ee
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fs
@@ -0,0 +1,36 @@
+module BracketsChecker
+
+open System
+
+/// Сhecks that the parentheses are correctly placed in the expression
+let bracketsChecker (str : String) =
+    let isNotBracket (ch : Char) =
+        ch <> '[' && ch <> '{' && ch <> '(' && ch <> ']' && ch <> '}' && ch <> ')'
+
+    /// Checks if symbol is a opening bracket
+    let isOpenBracket (bracket : Char) =
+        bracket = '[' || bracket = '{' || bracket = '('
+
+    /// Checks if symbols are opening and closing brackets of the same type
+    let isMatchingBrackets (first : Char) (second : Char) =
+        match first with
+        | '(' -> second = ')'
+        | '[' -> second = ']'
+        | '{' -> second = '}'
+        | _ -> true
+
+    /// Checks if brackets in line are correct
+    let rec checkLine (str : List<Char>) (memory : List<Char>) =
+        if str = []
+            then memory = []
+        else
+            let current = List.head str
+            if (isNotBracket current) then
+                checkLine (List.tail str) (memory)
+            elif (isOpenBracket current) then
+                checkLine (List.tail str) (current :: memory)
+            elif (memory <> [] && isMatchingBrackets (List.head memory) (current)) then
+                checkLine (List.tail str) (List.tail memory)
+            else false
+
+    checkLine (Seq.toList str) []
\ No newline at end of file
diff --git a/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fsproj b/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fsproj
new file mode 100644
index 0000000..d540876
--- /dev/null
+++ b/semester4/BracketsChecker/BracketsChecker/BracketsChecker.fsproj
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <Compile Include="BracketsChecker.fs" />
+    </ItemGroup>
+
+</Project>