#include<bits/stdc++.h>
using namespace std;
long long n;
long long sum[15];
string s;
int main() {
		cin >> n >> s;
		long long ans = 0;
		for (long long i = 0; i < s.size(); i++) {
			if (!(s[i] >= '0' && s[i] <= '9')) {
				sum[i] = s[i] - 'A' + 10;
			} else {
				sum[i] = s[i] - '0';
			}
			ans = ans * n + sum[i];
		}
		cout << ans;

	return 0;
}