# -*- coding: utf-8 -*-

A,B = input().split()

if len(A) > len(B):
    print(A)
elif len(A) < len(B):
    print(B)
else:
    for a,b in zip(A,B):
        a = int(a)
        b = int(b)
        if a==7 and b==4:
            print(B)
            break
        elif a==4 and b==7:
            print(A)
            break
        else:
            if a > b:
                print(A)
                break
            elif a < b:
                print(B)
                break
            else:
                continue