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For two strings s and t, we say "t divides s" if and only if s = t + ... + t  (t concatenated with itself 1 or more times)

Given two strings str1 and str2, return the largest string x such that x divides both str1 and str2.

 

Example 1:

Input: str1 = "ABCABC", str2 = "ABC"
Output: "ABC"

Example 2:

Input: str1 = "ABABAB", str2 = "ABAB"
Output: "AB"

Example 3:

Input: str1 = "LEET", str2 = "CODE"
Output: ""

Example 4:

Input: str1 = "ABCDEF", str2 = "ABC"
Output: ""

 

Constraints:

  • 1 <= str1.length <= 1000
  • 1 <= str2.length <= 1000
  • str1 and str2 consist of English uppercase letters.

class Solution { public String gcdOfStrings(String str1, String str2) { } }