#include <bits/stdc++.h>
using namespace std;
const int MOD = 998244353;
const int N = 5000 + 3;
vector<vector<long long>> C(N, vector<long long>(N, 0));
inline void init() {
  for (int n = 0; n < N; ++n) {
    C[n][0] = 1;
  }
  for (int n = 1; n < N; ++n) {
    for (int k = 1; k <= n; ++k) {
      C[n][k] = (C[n - 1][k] + C[n - 1][k - 1]) % MOD;
    }
  }
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  init();
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  vector<int> pref(n + 1, 0);
  for (int i = 0; i < n; ++i) {
    s[i] -= '0';
    pref[i + 1] = pref[i] + s[i];
  }
  long long ans = 1;
  if (pref.back() >= k) {
    for (int i = 0; i < n; ++i) {
      for (int j = i + 1; j < n; ++j) {
        vector<int> cnt = {0, 0};
        cnt[1] = pref[j + 1] - pref[i];
        if (cnt[1] > k) {
          continue;
        }
        cnt[0] = j - i + 1 - cnt[1];
        if (cnt[s[i] ^ 1]-- == 0) {
          continue;
        }
        if (cnt[s[j] ^ 1]-- == 0) {
          continue;
        }
        int d = C[j - i - 1][cnt[0]];
        ans = (ans + d) % MOD;
      }
    }
  }
  cout << ans;
  return 0;
}
