#pragma GCC optimize ("O2")
#pragma GCC target ("avx")
#include<bits/stdc++.h>
#include<iostream>
#include<cstring>
//#include<atcoder/all>
//using namespace atcoder;


using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Would
#define you
#define please



int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);


	int A;
	cin >> A;
	string B;
	cin >> B;

	int N = B.size();

	const int mod = 1e9 + 7;
	ll kotae = 0;
	ll kari = A - 1;
	rep(i, N - 1) {
		kotae += i * kari % mod;
		kari = kari * A % mod;
	}
	
	ll k = B[0] - '1';
	rep1(i, N - 1) {
		k = k * A + (B[i] - '0');
		k %= mod;
	}
	kotae += (k + 1) * (N - 1);

	co(kotae% mod);
	

	Would you please return 0;
}