#include <iostream>
using namespace std;
long t,a=-1;
main(){
    cin>>t;
	while(t--){
		string s;cin>>s;
		long z=0,q=1;int m=2,i=0;
		for(;s.size()>i;i++)m=max(m,s[i]-(s[i]<='9'?47:54));--i;
		for(;0<=i;i--)z+=q*(s[i]-(s[i]<='9'?48:55)),q*=m;
		a=min(z,(a==-1?z:a));
	}
	cout << a << endl;
}