import itertools
class Solution(object):
    def longestCommonPrefix(self, strs):
        """
        :type strs: List[str]
        :rtype: str
        """
        prefix=""
        for i in itertools.izip(*strs):
            s= "".join(i)
            if len(s)!=s.count(s[0]):
                break
            prefix+=s[0]
        return prefix