def longestCommonPrefix(strs):
    s = min(strs, key=len)
    prefix = []
    for i in range(len(s)):
        for j in range(i,len(s)):
            prefix.append(s[i:j+1])
    max_k = 0
    f_p = ''
    for i in prefix:
        k = 0
        for  j in strs:
            if j!=s:
                if i in j:
                    k+=1
                else: break
        if k==len(strs)-1:
            if max_k<len(i):
                max_k=len(i)
                f_p = i

    if max_k>0:
        return f_p
    else:
        return ""