#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, i, j, k, l, c = 0, ck = 0;
  cin >> n >> k;
  string st;
  cin >> st;
  for (i = 0; i < st.size(); i++) {
    if (st[i] == '#') {
      c = 0;
      for (j = i, ck = 0; ck != k; j++, ck++) {
        if (st[j] == '#')
          c++;
        else {
          break;
        }
      }
      if (c == k) {
        cout << "NO" << endl;
        return 0;
      } else {
        i = j - 1;
      }
    }
  }
  cout << "YES" << endl;
  return 0;
}
