#include <bits/stdc++.h>
using namespace std;
const int MAX = 100010;
int N, K;
string s;
int main() {
  ios::sync_with_stdio(false);
  cin >> N >> K;
  cin >> s;
  int v = 0;
  for (int i = 0, j; i < N; i = j) {
    j = i + 1;
    if (s[i] == '.') continue;
    while (j < N && s[i] == s[j]) ++j;
    v = max(v, j - i);
  }
  if (v >= K)
    cout << "NO\n";
  else
    cout << "YES\n";
  return 0;
}
