class Solution:
    def strStr(self, haystack: str, needle: str) -> int:
        nee_len = len(needle)
        hay_len = len(haystack)
        if nee_len > hay_len:
            return -1
        for i in range(hay_len - nee_len + 1):
            for j in range(nee_len):
                if haystack[i + j] != needle[j]:
                    break
            else:
                return i
        return -1

sol = Solution()
print("Output is :- ",sol.strStr("sadbutsad","sad"))
print("Output is :- ",sol.strStr("leetcode","leeto"))
print("Output is :- ",sol.strStr("safbutsadasf","sad"))

Output is :-  0
Output is :-  -1
Output is :-  6