#include <bits/stdc++.h>

typedef long long ll;
using namespace std;
int const INF = 1e9;

int to_int(string s) {
    int res = 0;
    for (char i : s) res = res * 10 + i - '0';
    return res;
}

int main()
{   ///mov eax shosh
    freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    ll n;
    cin >> n;
    string k;
    cin >> k;
    ll ans = 0;
    int cur = 0;
    for (char i : k) {
        int q = i - '0';
        if (cur * 10 + q < n) {
            cur = cur * 10 + q;
        } else {

        }
    }
    unsigned ll ans1 = 0;
    string cr = "";
    vector <int> ms; ms.clear();
    for (int i = k.size() - 1; i >= 0; i--) {
        if (k[i] == '0') {
            if (cr.size()) ms.push_back(to_int(cr));
            cr = "0";
            continue;
        }
        if (to_int(k[i] + cr) < n) {
            cr = k[i] + cr;
        } else {
            ms.push_back(to_int(cr));
            cr = k[i];
        }
    }
    ms.push_back(to_int(cr));
    for (int i = ms.size() - 1; i >= 0; i--) {
        ans1 = ans1 * n + ms[i];
       // cout << ms[i];
    }
    cout << min(ans, ans1);
    return 0;
}