def compare(a, b):
    if (a, b) == (4, 7):
        return -1
    elif (a, b) == (7, 4):
        return 1
    elif a < b:
        return 1
    elif a > b:
        return -1
    else:
        return 0

A, B = raw_input().split(' ')
if len(A) > len(B):
    print(A)
    quit()
if len(B) > len(A):
    print(B)
    quit()

for i in range(len(A)):
    a, b = map(lambda x: int(x[i]), (A, B))
    c = compare(a, b)
    if c == 1:
        print(B)
        quit()
    if c == -1:
        print(A)
        quit()