import sys
#sys.setrecursionlimit(n)
import heapq
import re
import bisect
import random
import math
import itertools
from collections import defaultdict, deque
from copy import deepcopy
from decimal import *

lm = lambda x: x - 55 if x >= 65 else x - 48
n = int(input())
e = [[int(lm(ord(i))) for i in list(input())] for i in range(n)]

num_base = 0
for ee in e:
    t = max(ee) + 1
    num_base = max(t, num_base)
ans = -1
for ee in e:
    t = 0
    num = 0    
    for ee2 in reversed(ee):
        t += pow(num_base, num) * ee2
        num += 1
    ans = min(ans, t) if ans >= 0 else t
print(ans)