from collections import Counter
N = input()
V = []
bases = []
for i in range(N):
    V.append(raw_input())

for i in range(2, 10):
    bases.append(i)
    
for i in range(ord('A'), ord('Z') + 2):
    bases.append(chr(i))
    
res = 1 << 80
for x in V:
    counter = Counter(x)
    for index,base in enumerate(bases):
        ok = True
        for y in map(str, bases[index:]):
            if (counter[y] > 0):
                ok = False
        if (ok):
            if (not str(base).isdigit()):
                res = min(res, int(x, ord(base) - ord('A') + 10))
            else:
                res = min(res, int(x, int(base)))

print res