#include <bits/stdc++.h>
using namespace std;
vector<int> a;
int k, t, n, mx;
string s;
int main() {
  cin >> n >> k;
  cin >> s;
  for (int i = 0; i < s.size(); i++)
    if (s[i] == '.') a.push_back(i);
  for (int i = 0; i < a.size() - 1; i++) mx = max(mx, a[i + 1] - a[i]);
  if (mx > k)
    cout << "NO";
  else
    cout << "YES";
}
