#include <bits/stdc++.h>
using namespace std;
int main() {
  double pos[4][2];
  double slope[4];
  bool zero[4];
  double temp;
  int lors;
  bool result;
  int i, j;
  char comma;
  while (cin >> pos[0][0]) {
    cin >> comma >> pos[0][1];
    for (i = 1; i < 4; i++) {
      for (j = 0; j < 2; j++) {
        cin >> comma >> pos[i][j];
      }
    }
    for (i = 0; i < 4; i++) {
      temp = pos[i % 4][0] - pos[(i + 1) % 4][0];
      if (temp == 0) {
        slope[i] = DBL_MAX;
        zero[i] = true;
      } else {
        slope[i] = (pos[i % 4][1] - pos[(i + 1) % 4][1]) / temp;
        zero[i] = false;
      }
    }
    result = true;
    for (i = 0; i < 2; i++) {
      cout << endl;
      if (slope[0] > slope[1]) {
        lors = 0;
      } else {
        lors = 1;
      }
      for (j = 1; j < 4; j++) {
        if (slope[j % 4] > slope[(j + 1) % 4] && !lors) {
          result = false;
          break;
        } else if (slope[j % 4] < slope[(j + 1) % 4] && lors) {
          result = false;
          break;
        } else {
          lors = 1 - lors;
        }
      }
      for (j = 0; j < 4; j++) {
        if (zero[j]) {
          slope[j] = DBL_MIN;
        }
      }
    }
    if (result) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
}
