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

const int N = 1002, mod = 1000000007;

long long dp[N][N][2];
char str[N];

int main()
{
	int n, k;
	scanf("%d %d", &n, &k);
	scanf("%s", str + 1);
	reverse(str + 1, str + n + 1);
	dp[0][0][0] = 1;
	for(int i = 1; i <= n; i++)
	{
		for(int j = 0; j <= k; j++)
		{
			if(str[i] == '1')
			{
				//0
				if(j > 0)
					dp[i][j][0] += dp[i-1][j-1][0];
				//1
				dp[i][j][1] += dp[i-1][j][0] + dp[i-1][j][1];
				//2
				if(j > 0)
					dp[i][j][1] += dp[i-1][j-1][1];
			}
			else
			{
				//0
				dp[i][j][0] += dp[i-1][j][0];
				//1
				if(j > 0)
					dp[i][j][0] += dp[i-1][j-1][1] + dp[i-1][j-1][0];
				//2
				dp[i][j][1] += dp[i-1][j][1];
			}
			dp[i][j][0] %= mod;
			dp[i][j][1] %= mod;
			//printf("%d %d: %d %d\n", i, j, dp[i][j][0], dp[i][j][1]);
		}
	}
	printf("%lld\n", (dp[n][k][0] + dp[n][k-1][1]) % mod);
}