import sys
import ast

def fun2(s):
    result = []
    for i in range(len(s)):
        for j in range(i + 1, len(s)):
            # 判断两个字符串是否有重复字符
            if len(set(s[i]) & set(s[j])) > 0:
                continue
            else:
                result.append(len(s[i]) * len(s[j]))
    return max(result) if result else 0

if __name__ == "__main__":
    for line in sys.stdin:
        s = line.strip()
        s = ast.literal_eval(s)
        print(fun2((s)))