#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;
using ll = long long;

ll modc = 1e9+7;

int main(){

    ll A, ans=0, base, N, C=0, base2=1;
    string B;
    cin >> A >> B;
    N = B.size();

    for (int i=0; i<N; i++) C = ((C * A) % modc + B[i]-'0') % modc;
    base = A-1;

    for (ll i=0; i<N-1; i++){
        ans += (base * i) % modc;
        base = (base * A) % modc;
        base2 = (base2 * A) % modc;
    }

    cout << (((N-1) * ((C+modc-base2) % modc + 1) % modc) + ans) % modc << endl;

    return 0;
}