#include <bits/stdc++.h>

#define REP(i, n) for(int (i)=0;(i)<(n);(i)++)
#define MOD 1000000007
#define LL long long

using namespace std;

char arr[2000];

int n = 0;
LL dp[2000][2000][2] = {};

LL get(int, int, int);

LL calc(int i, int j, int k){
    if (j == 0) {
        if (k == 0) {
            if (arr[n-i] == '0') return get(i-1, j, 0);
            else return 0;
        }
        else {
            if (arr[n-i] == '0') return get(i-1, j, 1);
            else return get(i-1, j, 1) + get(i-1, j, 0);
        }
    }
    if (k == 0) {
        if (arr[n-i] == '0') return get(i-1, j, 0) + get(i-1, j-1, 0) + get(i-1, j-1, 1);
        else return get(i-1, j-1, 0);
    }
    else {
        if (arr[n-i] == '0') return get(i-1, j, 1);
        else return get(i-1, j, 1) + get(i-1, j, 0) + get(i-1, j-1, 1);
    }
}

LL get(int i, int j, int k){
    return dp[i][j][k] % MOD;
}

int main(){
    dp[0][0][0] = 1;

    int k;
    cin >> n >> k;
    cin >> arr;

//    for(int i=1; i<2000; i++){
//        if (arr[n-1-i] == '0') {
//            dp[i][0][0] = dp[i-1][0][0];
//            dp[i][0][1] = dp[i-1][0][0];
//        } else {
//            dp[i][0][0] = 0;
//            dp[i][0][1] = 1;
//        }
//    }

    if(arr[n-1] == '0') {
        dp[1][0][0] = 1;
        dp[1][0][1] = 0;
        dp[1][1][0] = 1;
        dp[1][1][1] = 0;
    } else {
        dp[1][0][0] = 0;
        dp[1][0][1] = 1;
        dp[1][1][0] = 1;
        dp[1][1][1] = 0;
    }

    for(int i=2; i<=n; i++){
        for(int j=0; j<=i; j++){
            dp[i][j][0] = calc(i, j, 0) % MOD;
            dp[i][j][1] = calc(i, j, 1) % MOD;
        }
    }

    /*for(int i=0;i<=n;i++){
        for(int j=0;j<=n;j++){
            cout << dp[i][j][0] << "\t";
        }
        cout << endl;
    }
    cout << endl;

    for(int i=0;i<=n;i++){
        for(int j=0;j<=n;j++){
            cout << dp[i][j][1] << "\t";
        }
        cout << endl;
    }*/

    cout << (get(n, k, 0) + get(n, k-1, 1)) % MOD << endl;
}