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

using ll=long long;
using ld=long double;
#define FOR(i, aa,bb) for(ll i=aa;i<(ll)bb; i++)
#define F(N) FOR(i, 0, N)
#define FF(N) FOR(j, 0, N)
#define aa first
#define bb second
#define PB push_back
#define MOD (1000000007)

ll dp[1007][1007][2];
vector<int> a;
ll r(ll i, ll k, bool t) {
  //cout << i << " " << k << " " << t << endl;
  if (i == 0 && a[0] == k && t) {
    return dp[i][k][t] = 1;
  }
  if (k < 0) return 0;
  if (dp[i][k][t] != -1) return dp[i][k][t];
  else if (i == 0 && a[0] == 1 && k == 0 && !t) return dp[i][k][t] = 1;
  else if (i == 0) return dp[i][k][t] = 0;

  ll res;
  if (t) {
    if (a[i] == 0) {
      res = r(i - 1, k, true);
    } else { // 1
      res = r(i-1, k-1, true);
    }
  } else {
    if (a[i] == 0) {
      res = r(i - 1, k, false)
            + r(i - 1, k - 1, false);
    } else { // 1
      res = r(i - 1, k - 1, false)
            + r(i - 1, k, false)
            + r(i - 1, k, true);
    }
  }
  res %= MOD;
  return dp[i][k][t] = res;
}

ll f(vector<int> aa, ll n, ll k, bool eq) {
  a = aa;
  /*for (int l = 0; l < a.size(); ++ l) { cout << a[l]; }
  cout << endl;*/
  F(1007)FF(1007) dp[i][j][0] = -1;
  F(1007)FF(1007) dp[i][j][1] = -1;

  ll res = r(n-1, k, false);
  /*cout << "----" << endl;
  cout << k << endl;
  FOR(l,0,2) {
    for (ll x = 0; x <= k; ++ x) {
    FF(n) {
      r(j, x, l);
      cout << dp[j][x][l] << ' ';
    }
    cout << endl;
  }
  cout << endl << endl;
  }*/
  return res;
}

int main() {
  ll n, k;
  cin >> n >> k;
  vector<int> in = vector<int>(n);
  F(n) {
    char t;
    cin >> t;
    in[i] = t - '0';
  }
  vector<int> ub(n+1);
  FOR(i,1,n+1) ub[i] = in[i-1];
  /*for (ll i = 1; i >= 0; i --) {
    if (ub[i] == 0) {
      ub[i] = 1;
      break;
    }
    else ub[i] = 0;
  }*/
  ub[0] = 1;
  //cout << "ub" << endl;
  /*for (int l = 0; l < ub.size(); ++ l) { cout << ub[l]; }
  cout << endl;
  for (int l = 0; l < a.size(); ++ l) { cout << a[l]; }
  cout << endl;*/
  ll res = f(ub, n+1, k, false) - f(in, n, k, false);
  cout << res%MOD << endl;
  return 0;
}