#include <bits/stdc++.h>
using namespace std;
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};
int main() {
  double point[8];
  char c;
  bool yes;
  while (cin >> point[0] >> c >> point[1] >> c >> point[2] >> c >> point[3] >>
         c >> point[4] >> c >> point[5] >> c >> point[6] >> c >> point[7]) {
    vector<bool> posi;
    yes = true;
    for (int i = 0; i < (int)(4); ++i) {
      double angle = point[i * 2] * point[(i * 2 + 2) % 8 + 1] -
                     point[i * 2 + 1] * point[(i * 2 + 2) % 8];
      if (angle > 0.0) {
        posi.push_back(true);
      } else if (angle < 0.0) {
        posi.push_back(false);
      }
    }
    if (posi[0] == posi[1] && posi[2] == posi[1] && posi[2] == posi[3])
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
