#include<bits/stdc++.h>
#include <iomanip>
using namespace std;
#define EPS (1e-10)
#define REP(i,n) for (int i =0; i < (n);i++)


typedef long double ld;
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<double,double> pdd;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef vector<vector<int> > vvi;
typedef vector<ii> vii;

const int MOD = 1000000007;

ll solve(vector<vector<vector<ll>>> &dp, vi &s, int n, int k, int c) {
//    cout << n << " "<< k << " " << c << endl;
//    cout << dp[n][k][c] << endl;
    if (k < 0) return 0;
    if (n < 0) return 0;
    if (dp[n][k][c] != -1) return dp[n][k][c];
    ll res = 0;
    if (s[n] == 1) {
        if (c == 0) {
            res = solve(dp, s, n-1, k-1, 0);
        } else {
            res = solve(dp, s, n-1, k, 1);
            res += solve(dp, s, n-1, k, 0);
            res %= MOD;
            res += solve(dp, s, n-1, k-1, 1);
            res %= MOD;
        }
    } else {
        if (c == 1) {
            res = solve(dp, s, n-1, k, 1);
        } else {
            res = solve(dp, s, n-1, k, 0);
            res += solve(dp, s, n-1, k-1, 1);
            res %= MOD;
            res += solve(dp, s, n-1, k-1, 0);
            res %= MOD;
        }
    }
    return dp[n][k][c] = res;
}
int main(int argc, char** argv) {
    ios::sync_with_stdio(false);
    int N, K; cin >> N >> K;
    vi s(N+1);
    char chi;
    REP(i, N) {
        cin >> chi;
        if (chi == '0') s[N-i] = 0;
        else s[N-i] = 1;
    }
    vector<vector<vector<ll>>> dp(N+1, vector<vector<ll>>(K+1, vector<ll>(2, -1)));
//    for(int i = 0; i <= N; ++i) {
//        for(int j = 0; j <= K; ++j) {
//            dp[i][j][0] = dp[i][j][1] = -1;
//        }
//    }
    // init
    for(int j = 0; j <= K; ++j) {
        dp[0][j][0] = dp[0][j][1] = 0;
    }
    dp[0][0][0] = 1;
    cout << ((solve(dp, s, N, K, 0) + solve(dp, s, N, K-1, 1)) %MOD) << endl;
    return 0;
}