#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr int Inf = 2000000010;
constexpr ll INF= 2000000000000000000;
constexpr ll MOD = 1000000007;
const double PI = 3.1415926535897;
typedef pair<ll,ll> P;
typedef pair<int,P> PP;

template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}

template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

ll mod(ll val, ll M) {
    ll res = val % M;
    if(res < 0) {
        res += M;
    }
    return res;
}

template<typename T>
T RS(T N, T P, T M){
    if(P == 0) {
        return 1;
    }
    if(P < 0) {
        return 0;
    }
    if(P % 2 == 0){
        ll t = RS(N, P/2, M);
        if(M == -1) return t * t;
        return t * t % M;
    }
    if(M == -1) {
        return N * RS(N,P - 1,M);
    }
    return N * RS(N, P-1, M) % M;
}

int main() {
    ll A;
    cin >> A;
    assert(2 <= A && A <= 10);
    string B;
    cin >> B;
    bool cnt = true;
    ll N = B.size();
    assert(1 <= N && N <= 100000);
    for(int i = 0;i < N;i++) {
        if(i == 0 && B.at(i) == '0') {
            cnt = false;
        }
        else if(i != 0 && !('0' <= B.at(i) && B.at(i) <= '0' + A - 1)) {
            cnt = false;
        }
    }
    assert(cnt);
    vector<ll> vec(N);
    for(int i = 0;i < N;i++) {
        vec.at(i) = (B.at(i) - '0');
    }
    reverse(vec.begin(),vec.end());
    ll ret = 0;
    for(ll i = 1;i < N;i++) {
        ret += (i - 1) * mod(RS(A,i,MOD) - RS(A,i - 1,MOD),MOD);
        ret %= MOD;
    }
    vec.at(N - 1)--;
    for(ll i = 0;i < N;i++) {
        ret += (N - 1) * vec.at(i) % MOD * RS(A,i,MOD) % MOD;
        ret %= MOD;
    }
    ret += N - 1;
    ret %= MOD;
    cout << ret << endl;
}