Your task is to implement the function strstr. The function takes two strings as arguments (s,x) and  locates the occurrence of the string x in the string s. The function returns and integer denoting the first occurrence of the string x in s (0 based indexing).

Example 1:

Input:
s = GeeksForGeeks, x = Fr
Output: -1
Explanation: Fr is not present in the
string GeeksForGeeks as substring.

Example 2:

Input:
s = GeeksForGeeks, x = For
Output: 5
Explanation: For is present as substring
in GeeksForGeeks from index 5 (0 based
indexing).

Your Task:
You don't have to take any input. Just complete the strstr() function which takes two strings str, target as an input parameter. The function returns -1 if no match if found else it returns an integer denoting the first occurrence of the x in the string s.

Expected Time Complexity: O(|s|*|x|)
Expected Auxiliary Space: O(1)

Note : Try to solve the question in constant space complexity.

Constraints:
1 <= |s|,|x| <= 1000