#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

long long md = 1000000007;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int a; string s; cin >> a >> s;
    int n = s.length();
    long long ans = 0, r = 1;
    for (int i = 1; i < n; i++) {
        ans = (ans + r * (s[n - i] - '0')) % md;
        r = (r * a) % md;
    }
    ans = ((ans + 1LL) * (n - 1)) % md;
    r = 1;
    for (int i = 1; i < n; i++) {
        ans = (ans + r * (a - 1) * (i - 1)) % md;
        r = (r * a) % md;
    }
    ans = (ans + (long long)(s[0] - '1') * (n - 1) * r) % md;
    cout << ans << '\n';
    return 0;
}