import java.io.*;
import java.util.*;

public class Main {
    static final int MOD = 1000000007;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int a = sc.nextInt();
        char[] arr = sc.next().toCharArray();
        int length = arr.length;
        long ans = 0;
        long all = 0;
        for (int i = 0; i < length; i++) {
            all *= a;
            all += arr[i] - '0';
            all %= MOD;
        }
        ans += (all - pow(a, length - 1) + 1 + MOD) % MOD * (length - 1) % MOD;
        
        for (int i = 1; i < length; i++) {
            ans += (pow(a, i) - pow(a, i - 1) + MOD) % MOD * (i - 1) % MOD;
            ans %= MOD;
        }
        System.out.println(ans);
    }
    
    static long pow(long x, int p) {
        if (p == 0) {
            return 1;
        } else if (p % 2 == 0) {
            return pow(x * x % MOD, p / 2);
        } else {
            return pow(x, p - 1) * x % MOD;
        }
    }
}


class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}