#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<bitset>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<deque>
#include<list>
#include<iomanip>
#include<cmath>
#include<cstring>
#include<functional>
#include<cstdio>
#include<cstdlib>
#include<numeric>
#include<ctime>
//#include<atcoder/all>
using namespace std;
//using namespace atcoder;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define INF 2e9
#define MOD 1000000007
//#define MOD 998244353
#define LINF (long long)4e18
#define jck 3.141592
#define PI acos(-1.0)

const double EPS = 1e-10;

using ll = long long;
using Pi = pair<int,int>;
using Pl = pair<ll,ll>;
//using mint = modint998244353;

int dh[] = {-1,0,1,0};
int dw[] = {0,1,0,-1};

ll modpow(ll a, ll n, ll m){
    if(n == 0) return 1;
    ll half = modpow(a,n/2,m);
    ll res = half * half % m;
    if(n & 1) res = res * (a%m) % m;
    return res;
}

int main(){
    int a; cin >> a;
    string b; cin >> b;
    reverse(b.begin(),b.end());
    int m = b.size();
    ll ans = 0;
    rep(i,m-1){
        ans += i*(a-1)*modpow(a,i,MOD)%MOD;
        ans %= MOD;
    }
    ll sum1 = 0,sum2 = 0;
    rep(i,m){
        sum1 += (b[i]-'0')*modpow(a,i,MOD)%MOD;
        sum1 %= MOD;
        if(i < m-1){
            sum2 += (a-1)*modpow(a,i,MOD)%MOD;
            sum2 %= MOD;
        }
    }
    ll sum = (sum1-sum2+MOD)%MOD;
    ans += sum*(m-1)%MOD;
    ans %= MOD;
    cout << ans << endl;
}