diff --git a/4/build.md b/4/build.md
new file mode 100644
index 0000000..3b81ce1
--- /dev/null
+++ b/4/build.md
@@ -0,0 +1,9 @@
+# Copy - Paste
+
+gcc -c optimal_sort.s -o optimal_sort.o
+
+gcc -c main.c -o main.o
+
+gcc main.o optimal_sort.o
+
+./a.out
diff --git a/4/main.c b/4/main.c
new file mode 100644
index 0000000..29ef0fe
--- /dev/null
+++ b/4/main.c
@@ -0,0 +1,33 @@
+#include "optimal_sort.h"
+
+void printArray(int size, int arr[]);
+
+void main()
+{
+    int arr[100];
+    int before[100];
+    int n = 0;
+
+    while (n < 100 && scanf("%d", &arr[n]) == 1) {
+        before[n] = arr[n];
+        n++;
+
+        if (getchar() == '\n') {
+            break;
+        }
+    }
+
+    printArray(n, arr);
+    int changes = sortArray(0, n, arr, 0);
+    printArray(n, arr);
+
+    printf("%d %d\n", n, changes);
+}
+
+void printArray(int size, int arr[])
+{
+    for (int i = 0; i < size; i++) {
+        printf("%d ", arr[i]);
+    }
+    printf("\n");
+}
diff --git a/4/optimal_sort.c b/4/optimal_sort.c
new file mode 100644
index 0000000..5efe359
--- /dev/null
+++ b/4/optimal_sort.c
@@ -0,0 +1,40 @@
+#include "optimal_sort.h"
+
+int sortArray(int start, int end, int arr[], int changes)
+{
+    if (end - start <= 1) {
+        return 0;
+    }
+
+    int pivot = arr[end - 1];
+    int left = start;
+    int right = end - 2;
+
+    while (left <= right) {
+        while (arr[left] <= pivot && left <= right) {
+            left++;
+        }
+
+        while (arr[right] > pivot && left <= right) {
+            right--;
+        }
+
+        if (left < right) {
+            int temp = arr[left];
+            arr[left] = arr[right];
+            arr[right] = temp;
+            left++;
+            right--;
+            changes += 2;
+        }
+    }
+
+    arr[end - 1] = arr[left];
+    arr[left] = pivot;
+
+    changes += 2;
+    changes += sortArray(start, left, arr, changes);
+    changes += sortArray(left + 1, end, arr, changes);
+
+    return changes;
+}
diff --git a/4/optimal_sort.h b/4/optimal_sort.h
new file mode 100644
index 0000000..04a5fed
--- /dev/null
+++ b/4/optimal_sort.h
@@ -0,0 +1,4 @@
+#pragma once
+#include <stdio.h>
+
+int sortArray(int start, int end, int arr[], int changes);
diff --git a/4/optimal_sort.s b/4/optimal_sort.s
new file mode 100644
index 0000000..c3585b8
--- /dev/null
+++ b/4/optimal_sort.s
@@ -0,0 +1,167 @@
+	.file	"optimal_sort.c"
+	.text
+	.globl	sortArray
+	.type	sortArray, @function
+sortArray:
+.LFB0:
+	.cfi_startproc
+	endbr64
+	pushq	%rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset 6, -16
+	movq	%rsp, %rbp
+	.cfi_def_cfa_register 6
+	subq	$48, %rsp
+	movl	%edi, -20(%rbp)
+	movl	%esi, -24(%rbp)
+	movq	%rdx, -32(%rbp)
+	movl	%ecx, -36(%rbp)
+	movl	-24(%rbp), %eax
+	subl	-20(%rbp), %eax
+	cmpl	$1, %eax
+	jg	.L2
+	movl	$0, %eax
+	jmp	.L3
+.L2:
+	movl	-24(%rbp), %eax
+	cltq
+	salq	$2, %rax
+	leaq	-4(%rax), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	(%rax), %eax
+	movl	%eax, -8(%rbp)
+	movl	-20(%rbp), %eax
+	movl	%eax, -16(%rbp)
+	movl	-24(%rbp), %eax
+	subl	$2, %eax
+	movl	%eax, -12(%rbp)
+	jmp	.L11
+.L7:
+	addl	$1, -16(%rbp)
+.L5:
+	movl	-16(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	(%rax), %eax
+	cmpl	%eax, -8(%rbp)
+	jl	.L8
+	movl	-16(%rbp), %eax
+	cmpl	-12(%rbp), %eax
+	jle	.L7
+	jmp	.L8
+.L10:
+	subl	$1, -12(%rbp)
+.L8:
+	movl	-12(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	(%rax), %eax
+	cmpl	%eax, -8(%rbp)
+	jge	.L9
+	movl	-16(%rbp), %eax
+	cmpl	-12(%rbp), %eax
+	jle	.L10
+.L9:
+	movl	-16(%rbp), %eax
+	cmpl	-12(%rbp), %eax
+	jge	.L11
+	movl	-16(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	(%rax), %eax
+	movl	%eax, -4(%rbp)
+	movl	-12(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	-16(%rbp), %edx
+	movslq	%edx, %rdx
+	leaq	0(,%rdx,4), %rcx
+	movq	-32(%rbp), %rdx
+	addq	%rcx, %rdx
+	movl	(%rax), %eax
+	movl	%eax, (%rdx)
+	movl	-12(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rax, %rdx
+	movl	-4(%rbp), %eax
+	movl	%eax, (%rdx)
+	addl	$1, -16(%rbp)
+	subl	$1, -12(%rbp)
+	addl	$2, -36(%rbp)
+.L11:
+	movl	-16(%rbp), %eax
+	cmpl	-12(%rbp), %eax
+	jle	.L5
+	movl	-16(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rdx, %rax
+	movl	-24(%rbp), %edx
+	movslq	%edx, %rdx
+	salq	$2, %rdx
+	leaq	-4(%rdx), %rcx
+	movq	-32(%rbp), %rdx
+	addq	%rcx, %rdx
+	movl	(%rax), %eax
+	movl	%eax, (%rdx)
+	movl	-16(%rbp), %eax
+	cltq
+	leaq	0(,%rax,4), %rdx
+	movq	-32(%rbp), %rax
+	addq	%rax, %rdx
+	movl	-8(%rbp), %eax
+	movl	%eax, (%rdx)
+	addl	$2, -36(%rbp)
+	movl	-36(%rbp), %ecx
+	movq	-32(%rbp), %rdx
+	movl	-16(%rbp), %esi
+	movl	-20(%rbp), %eax
+	movl	%eax, %edi
+	call	sortArray
+	addl	%eax, -36(%rbp)
+	movl	-16(%rbp), %eax
+	leal	1(%rax), %edi
+	movl	-36(%rbp), %ecx
+	movq	-32(%rbp), %rdx
+	movl	-24(%rbp), %eax
+	movl	%eax, %esi
+	call	sortArray
+	addl	%eax, -36(%rbp)
+	movl	-36(%rbp), %eax
+.L3:
+	leave
+	.cfi_def_cfa 7, 8
+	ret
+	.cfi_endproc
+.LFE0:
+	.size	sortArray, .-sortArray
+	.ident	"GCC: (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0"
+	.section	.note.GNU-stack,"",@progbits
+	.section	.note.gnu.property,"a"
+	.align 8
+	.long	1f - 0f
+	.long	4f - 1f
+	.long	5
+0:
+	.string	"GNU"
+1:
+	.align 8
+	.long	0xc0000002
+	.long	3f - 2f
+2:
+	.long	0x3
+3:
+	.align 8
+4: