#include <bits/stdc++.h>
using namespace std;
using ll = long long;
vector<string> s(100, string(100, '.'));
int n, k;
int solve() {
  ios::sync_with_stdio(false), cin.tie(0);
  cin >> n >> k;
  if (n - 2 == k) {
    for (int i = 1; i < n - 1; i++) {
      s[1][i] = '#';
    }
    return 1;
  }
  if (k % 2 == 0) {
    for (int j = 0; j < n; j++) {
      for (int i = 0; i < 4; i++) {
        if (i != 0 && i != 3 && j != 0 && j != n - 1 && k) {
          s[i][j] = '#';
          k--;
        }
      }
    }
    return 1;
  }
  if (k >= 5) {
    s[1][1] = '#';
    s[2][1] = '#';
    k -= 2;
    for (int i = 2; i < n - 2; i++) {
      s[1][i] = '#';
      k--;
      if (k == 2) {
        s[1][i + 1] = s[2][i + 1] = '#';
        return 1;
      }
    }
    s[1][n - 2] = s[2][n - 2] = '#';
    k -= 2;
    for (int i = 2; i < n - 2; i++) {
      s[2][i] = '#';
      k--;
      if (k == 0) return 1;
    }
  }
  if (k == 3) {
    s[1][n / 2 + 1] = s[2][n / 2] = s[1][n / 2 - 1] = '#';
    return 1;
  }
  if (k == 1) {
    s[2][n / 2] = '#';
    return 1;
  }
  assert(0);
}
int main() {
  int t = solve();
  if (!solve()) return (cout << "NO" << endl, 0);
  cout << "YES" << endl;
  for (int i = 0; i < 4; i++) {
    for (int j = 0; j < n; j++) {
      cout << s[i][j];
    }
    cout << endl;
  }
}
