#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

//val(base-X) -> val(base-10);
long long base_X_to_decimal(string val, int X){
	long long ret = 0;
	long long k = 1;
	for(int i=val.size()-1; i>=0; i--){
		int tmp;
		if('0'<= val[i] && val[i] <= '9'){
			tmp = val[i] - '0';
		}else if('A' <= val[i] && val[i] <= 'Z'){
			tmp = val[i] - 'A' +10;
		}else if('a' <= val[i] && val[i] <= 'z'){
			tmp = val[i] - 'a' +10;
		}else{
			tmp = -1;
		}

		//assert(tmp>=0);

		if(tmp >= X) return -1;
		ret += tmp * k;
		k *= X;
	}
	return ret;
}

long long convert_to_d(string s){
	int base = *max_element(s.begin(),s.end()) - '0';
	if(base > 10) base = base - ('A' - ':');
	base = max(2, base+1);

	//cerr << s << " " << base << endl;

	long long ret = base_X_to_decimal(s, base);

	return ret;
}

int main(){
	int N;
	cin >> N;

	vector<string> v(N);
	for(int i=0; i<N; i++){
		cin >> v[i];
	}

	vector<long long> ans(N);
	for(int i=0; i<N; i++){
		ans[i] = convert_to_d(v[i]);
		//cerr << ans[i] << endl;
	}

	cout << (*min_element(ans.begin(), ans.end())) << endl;

	return 0;
}