#include <bits/stdc++.h>
using namespace std;
typedef struct {
  double x;
  double y;
} Point;
const int INF = (1 << 25);
Point p[4];
double m[4];
void make() {
  for (int i = 0; i < 4; i++) {
    if (p[i].x - p[(i + 1) % 4].x)
      m[i] = (p[i].y - p[(i + 1) % 4].y) / (p[i].x - p[(i + 1) % 4].x);
    else
      m[i] = INF;
  }
}
int solve() {
  make();
  if (m[0] == m[2] && m[1] == m[3]) return 1;
  return 0;
}
int main() {
  int status = 0;
  while (1) {
    char t;
    for (int i = 0; i < 3; i++)
      if (!(cin >> p[i].x >> t >> p[i].y >> t)) status = 1;
    if (status) break;
    if (!(cin >> p[3].x >> t >> p[3].y)) status = 1;
    if (status) break;
    if (solve())
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
  return 0;
}
