#include <bits/stdc++.h>
using namespace std;
char s[300005];
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n, m, cnt, mx = 0;
  cin >> n >> m >> s;
  if (s[n - 1] == '#') {
    cout << "NO" << '\n';
    return 0;
  }
  for (int i = 0; i < n; ++i) {
    if (s[i] == '#')
      ++cnt;
    else
      cnt = 0;
    mx = max(mx, cnt);
  }
  if (m <= mx)
    cout << "NO" << '\n';
  else
    cout << "YES" << '\n';
}
