#include "bits/stdc++.h"
#include "atcoder/all"
using namespace std;
using namespace atcoder;
using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int a; cin >> a;
	string b; cin >> b;
	mint ans = 0;
	int n = b.size();
	mint l = 1;
	mint r = a;
	rep(i, n - 1) {
		ans += i * (r - l);
		l = r;
		r *= a;
	}
	mint sub = 0;
	rep(i, b.size()) {
		sub *= a;
		sub += b[i] - '0';
		if (0 != i)sub -= a - 1;
	}
	ans += sub * (b.size() - 1);
	cout << ans.val() << endl;
	return 0;
}