#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  string s;
  cin >> s;
  int i = 0;
  int flag = 0;
  while (i < n - 1) {
    int j = 1;
    while (j <= k) {
      if (s[i + j] != '#') {
        i = i + j;
        break;
      } else if (j == k && s[i + j] != '.') {
        flag = 1;
        break;
      }
      j++;
    }
    if (flag == 1) {
      break;
    }
  }
  if (i == n - 1 && flag == 0) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  return 0;
}
