# coding: utf-8
#yuki_164

import sys

def base_convert(nl, ibase, obase):
    o = []
    while any(nl):
        c = 0
        for i in xrange(len(nl)):
            c = c * ibase + nl[i]
            nl[i],c = divmod(c,obase)
        o.append(c)
    o.reverse()
    return o

def radix(lst):
 rdx=0
 for i in xrange(len(lst)):
  order=ord(lst[i])
  if order>=48 and order<=57:
   tmp=order-47
   if tmp>rdx:
    rdx=tmp
  elif order>=65 and order<=90:
   tmp=order-54
   if tmp>rdx:
    rdx=tmp
 return rdx

n=int(raw_input())
res=sys.maxint
for i in xrange(n):
 s=raw_input()
 ls=map(str,s)
 ls2=[]
 for i in xrange(len(ls)):
  if s[i].isalpha()==False:
   ls2.append(int(s[i]))
  elif s[i].isalpha()==True:
   ls2.append(ord(s[i])-55)
 rdx=radix(ls)
 ls3=base_convert(ls2,rdx,10)
 rest=int("".join(map(str,ls3)))
 if rest<res:
  res=rest

print res