#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

#include<atcoder/modint>
using mint = atcoder::modint1000000007;

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll a;
    string b;
    cin>>a>>b;
    mint ans = 0;
    int m = b.size();
    for(int i = 1;i<m;i++){
        mint tmp = mint(a-1) * mint(a).pow(i-1);
        ans += mint(i-1) * tmp;
    }
    mint tmp = mint(a).pow(m-1);
    mint sum = 0;
    for(int i = 0;i<b.size();i++){
        sum *= a;
        sum += b[i] - '0';
    }
    ans += mint(m-1) * (sum-tmp+1);
    cout<<ans.val()<<endl;
}