#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int A;
string B;

int main(){
	
	cin>>A>>B;
	
	mint sum = 0;
	rep(i,B.size()){
		sum *= A;
		sum += B[i] - '0';
	}
//	cout<<sum.val()<<endl;
	mint ans = 0;
	
	mint cur = A-1;
	
	rep(i,B.size()-1){
		sum -= cur;
		ans += sum;
		cur *= A;
	}
	
	cout<<ans.val()<<endl;
	
    return 0;
}