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(); } }