#include<stdio.h>
int main()
{
	long long int a;
	scanf("%lld", &a);
	char b[100005];
	scanf("%s", b);
	long long int p = 1000000007;
	long long int n = 0;
	while (b[n] != '\0')
		n++;
	long long int ans = 0;
	long long int i, j, k;
	for (i = 0, j = 1; i < n - 1; i++, j = j * a % p)
		ans = (ans + i * j % p * (a - 1) % p) % p;
	for (i = n - 1, j = 1, k = 1; i > 0; i--, k = k * a % p)
		j = (j + k * (b[i] - '0') % p) % p;
	j = (j + (b[0] - '1') * k % p) % p;
	printf("%lld\n", (ans + (n - 1) * j % p) % p);
	return 0;
}