#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <cmath>   
#include<cctype>
#include<string>
#include<set>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
#define all(x) (x).begin(),(x).end()
#define rep(i,m,n) for(int i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(int i = m;i >= n;--i)
#define INF INT_MAX/2
using namespace std;
using ll = long long;
using R = double;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 50;
struct edge { ll from; ll to; ll cost; };

ll ans = -1;
ll n;
ll convert(string s) {
	ll ret = 0;
	ll p = -1;
	rep(i, 0, s.size()) {
		ll temp = -1;
		if (0 <s[i] - '0' && s[i] - '0' <= 9) {
			temp = (ll)(s[i] - '0') + 1;
		}
		else {
			temp = (ll)(s[i] - 'A') + 11LL;
		}
		p = max(p,temp);
	}
	if (p == -1)return 0;

	reverse(all(s));
	ll pow = 1;
	rep(i, 0, s.size()) {
		if (0 <= s[i] - '0' && s[i] - '0' <= 9) {
			ret += ((ll)(s[i] - '0'))*pow;
		}
		else {
			ret += ((ll)(s[i] - 'A') + 10LL)*pow;
		}
		pow *= p;
	}
	return ret;
}

int main(){
	cin >> n;

	rep(i,0,n) {
		string s;
		cin >> s;
		ll temp = convert(s);
		if (ans == -1)ans = temp;
		else ans = min(temp,ans);
	}
	cout << ans << endl;

	return 0;
}