#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(i,a,n) for (int i = (a); i < (n); i++)
#define per(i,a,n) for (int i = (n) - 1; i >= (a); i--)

const ll MOD = 1e9 + 7;

const int N = 2018;

ll nck[N][N];

void add(ll& a, ll b) {
    a = (a + b) % MOD;
}

int main(void)
{
	ios_base::sync_with_stdio(false);
	int n, k;
	cin >> n >> k;
	string s;
	cin >> s;

    nck[0][0] = 1;
    rep(i,0,N-1) rep(j,0,N-1) {
        add(nck[i+1][j], nck[i][j]);
        add(nck[i+1][j+1], nck[i][j]);
    }

    //vector<bool> a(n + 1);
    //rep(i,0,n) a[i+1] = s[i] == '1';
    vector<bool> a(n);
    rep(i,0,n) a[i] = s[i] == '1';
    n = a.size();

    // rep(i,0,a.size()) cout << a[i];

    ll res = 0;

    rep(i,0,n) {
        if (a[i]) {
            if (k >= 1) {
              //  cout << "x" << i << " " << nck[n-i-1][k-1] << endl;
                add(res, nck[n-i-1][k-1]);
            }
            k--;
        } else {
            if (k >= 1) {
          //      cout << i << " " << nck[n-i-1][k] << endl;
                add(res, nck[n-i-1][k-1]);
            }
        }
    }
    if (k == 0) add(res, 1);

    cout << res << endl;
}