digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
N = input()
numbers = []
for i in xrange(N):
    numbers.append(raw_input())
min_num = float("inf")
for s in numbers:
    #decimal_digits = [digits.index(x) for x in s]
    decimal_digits = [digits.find(x) for x in s]
    base = max(decimal_digits)+1
    temp_num = int(s, base)
    if temp_num <= min_num:
        min_num = temp_num
print min_num