#include <bits/stdc++.h>
using namespace std;
int isConvex(double ax, double ay, double ox, double oy, double bx, double by) {
  double x1 = ax - ox;
  double y1 = ay - oy;
  double x2 = bx - ox;
  double y2 = by - oy;
  double angle;
  angle =
      (x1 * x2 + y1 * y2) / (sqrt(x1 * x1 + y1 * y1) * sqrt(x2 * x2 + y2 * y2));
  if (angle < 0.0f) return 1;
  return 0;
}
int main() {
  float ax, ay, bx, by, cx, cy, dx, dy;
  while (
      scanf("%f,%f,%f,%f,%f,%f,%f,%f", &ax, &ay, &bx, &by, &cx, &cy, &dx, &dy) +
      1) {
    if (isConvex(ax, ay, bx, by, cx, cy) | isConvex(bx, by, cx, cy, dx, dy) |
        isConvex(cx, cy, dx, dy, ax, ay) | isConvex(dx, dy, ax, ay, bx, by))
      cout << "NO" << endl;
    else
      cout << "YES" << endl;
  }
  return 0;
}
