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

#define rep(i,n) for(int i=0; i<(n); ++i)
#define st first
#define nd second
#define pb push_back
#define mp make_pair

typedef vector<int> vi;
typedef pair<int,int> pii;
typedef long long ll;
const int maxn = 1005;
char x[maxn];
int dp[maxn][maxn][2];
const int mod = 1000000007;
void solve() {
	int n, k;
	scanf("%d %d", &n, &k);
	scanf(" %s", x);
	dp[n][0][0] = 1;
	int zap = 0;
	for(int i = n; i; i --){
		for(int j = 0; j <= zap; j ++){
			for(int k = 0; k < 2; k ++){
				int a = (x[i - 1] == '1') + k; // nie zapalam tego bitu i - 1
				dp[i - 1][j + a%2][a/2] += dp[i][j][k];
				if(dp[i - 1][j + a%2][a/2] >= mod) dp[i - 1][j + a%2][a/2] -= mod;
				a ++; //zapalam bit i - 1
				dp[i - 1][j + a%2][a/2] += dp[i][j][k];
				if(dp[i - 1][j + a%2][a/2] >= mod) dp[i - 1][j + a%2][a/2] -= mod;
			}
		}
		zap ++;
	}
	printf("%d\n", (dp[0][k][0] + dp[0][k-1][1])%mod);
}

int main(){
solve();
return 0;
}