#include <bits/stdc++.h>
using namespace std;
struct p {
  double x;
  double y;
};
int check(struct p a, struct p b, struct p c, struct p d) {
  if (((a.x - b.x) * (c.y - a.y) + (a.y - b.y) * (a.x - c.x)) *
      ((a.x - b.x) * (d.y - a.y) + (a.y - b.y) + (a.x - d.x))) {
    return 1;
  }
  return 0;
}
int main() {
  double x1, x2, x3, x4, y1, y2, y3, y4;
  while (scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &x1, &y1, &x2, &y2, &x3, &y3,
               &x4, &y4) != EOF) {
    p a, b, c, d;
    a.x = x1, a.y = y1;
    b.x = x2, b.y = y2;
    c.x = x3, c.y = y3;
    d.x = x4, d.y = y4;
    if (check(a, c, b, d) && check(b, d, a, c)) {
      cout << "NO";
    } else {
      cout << "YES";
    }
    cout << endl;
  }
  return 0;
}
