class Solution:
    def commonPrefixUtil(self,str1, str2): 
  
        result = ""; 
        n1 = len(str1) 
        n2 = len(str2) 
  
    # Compare str1 and str2 
        i = 0
        j = 0
        while i <= n1 - 1 and j <= n2 - 1: 
      
            if (str1[i] != str2[j]): 
                break
              
            result += str1[i] 
            i += 1
            j += 1
  
        return (result) 
    def longestCommonPrefix(self, A):
        prefix = A[0] 
  
        for i in range (1, len(A)): 
            prefix = Solution().commonPrefixUtil(prefix, A[i]) 
  
        return (prefix)
        
                
            
        # write your method here