diff --git a/easy/day_20/problem.txt b/easy/day_20/problem.txt
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+Imagine you're handed a positive integer  n . 
+
+Your task is to construct a permutation  a1, a2, . . ., an  such that for any pair of indices  l  and  r  where  1 ≤ l < r ≤ n , the sum  al + a{l+1} + . . . + ar  is never divisible by  r - l + 1 .
+
+In simpler terms, you need to create a sequence where no consecutive subsequence of elements sums up to a number divisible by the length of that subsequence plus one.
+
+For instance, if  n = 5 , a valid permutation could be  [3, 2, 5, 4, 1]  because:
+-  3 + 2 = 5  is not divisible by  2 + 1 = 3 ,
+-  2 + 5 = 7  is not divisible by  2 + 1 = 3 ,
+-  5 + 4 = 9  is not divisible by  2 + 1 = 3 , and so on.
+
+Input:
+- The number of test cases  t  ( 1 ≤ t ≤ 100 ).
+- For each test case: an integer  n  ( 1 ≤ n ≤ 100 ), the size of the permutation.
+
+Output:
+- If no such permutation exists, print -1.
+- Otherwise, print  n  distinct integers  p1, p2, . . ., pn  ( 1 ≤ pi ≤ n ) representing a permutation satisfying the given condition. If multiple solutions exist, any valid permutation is acceptable.
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diff --git a/easy/day_20/sample_test_cases.txt b/easy/day_20/sample_test_cases.txt
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+Example
+
+input
+3
+1
+2
+3
+output
+1
+1 2
+-1
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diff --git a/easy/day_20/solution.cpp b/easy/day_20/solution.cpp
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+//write your code here
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