#include <bits/stdc++.h>
using namespace std;
long long i, j, n, c[123456], a[1111234], b[1125678], d[123456], l, ll, r, s, t,
    k, m, xh, x, x1, y, z;
string p, q;
map<long long, long long> mm;
int main() {
  cin >> n >> m >> p;
  for (i = 0; i < n; i++) {
    if (p[i] == '#')
      t++;
    else {
      s = max(s, t);
      t = 0;
    }
  }
  if (s >= m)
    cout << "NO";
  else
    cout << "YES";
  return 0;
}
