#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:16777216")
using namespace std;
int main() {
  int n, k;
  cin >> n >> k;
  string s;
  while (s.empty()) cin >> s;
  reverse((s).begin(), (s).end());
  int lastEmpty = 0;
  s[0] = 'C';
  for (int i = 0; i < n - 1; i++) {
    if (s[i] == 'C') {
      for (int j = lastEmpty; j < n && j <= i + k; j++) {
        if (s[j] == '.') {
          s[j] = 'C';
        }
      }
      lastEmpty = i + k + 1;
    }
  }
  if (s[n - 1] == 'C')
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
