#include <bits/stdc++.h>
using namespace std;

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

#include <atcoder/modint>
using mint = atcoder::modint1000000007;

int main() {
    int a; cin >> a;

    auto [b, l] = [&] {
        string s; cin >> s;

        mint b = 0;
        for (auto c : s) {
            b *= a;
            b += c - '0';
        }

        return make_tuple(b, size(s));
    }();

    mint ans = 0, acc = 1;
    for (int i = 1; i < l; ++i) {
        acc *= a;
        ans += b - (acc - 1);
    }

    cout << ans.val() << endl;
}