INF = 1 << 64
N = int(input())
V = [input() for _ in range(N)]

ans = INF
for v in V:
    c = max(v)
    if c.isdigit():
        b = int(c) + 1
    else:
        b = ord(c) - ord('A') + 11

    ans = min(ans, int(v, b))

print(ans)