import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
        int n = koko.nextInt();
        String[] moto = new String[n];
        long[] chicchai = new long[n];
        for(int i=0; i<n; i++){
            moto[i] = koko.next();
            chicchai[i] = parse(moto[i], 'Z', 36);
        }
        Arrays.sort(chicchai);
        System.out.println(chicchai[0]);
    }
    static long parse(String moto, char sinsu, int sin){
        String s = String.valueOf(sinsu);
        if(moto.indexOf(s)!=-1){
            long a = Long.parseLong(moto, sin);
            return a;
        }else if(sinsu=='A'){
            return parse(moto, '9', 10);
        }else{
            return parse(moto, (char)(sinsu-1), sin-1);
        }
    }
}