#include <bits/stdc++.h>
using namespace std;

typedef long double ld;

const ld EPS = 1e-9;
const ld INF = 1e10;
const ld PI = M_PI;

struct Point{
  ld x, y;
  Point(ld x, ld y):x(x), y(y){}
  Point(){}
};

Point operator+(const Point &a, const Point &b){
  return Point(a.x + b.x, a.y + b.y);
}
Point operator-(const Point &a, const Point &b){
  return Point(a.x - b.x, a.y - b.y);
}
Point operator*(const Point &a, const ld b){
  return Point(a.x * b, a.y * b);
}
Point operator*(const Point &a, const Point &b){
  return Point(a.x*b.x-a.y*b.y, a.x*b.y+a.y*b.x);
}
Point operator/(const Point &a, const ld b){
  return Point(a.x / b, a.y / b);
}

typedef vector<Point> Polygon;

Point next(const Polygon &a, int x){
  return a[(x+1)%a.size()];
}
Point prev(const Polygon &a, int x){
  return a[(x-1+a.size()) % a.size()];
}

ld cross(const Point &a, const Point &b){
  return a.x*b.y - a.y*b.x;
}

ld dot(const Point &a, const Point &b){
  return a.x*b.x + a.y*b.y;
}
ld norm(const Point &a){
  return dot(a, a);
}

int ccw(Point a, Point b, Point c){
  b = b - a;
  c = c - a;
  if(cross(b, c) > EPS) return +1; // 反時計周り
  if(cross(b, c) < -EPS) return -1; // 時計周り
  if(dot(b, c) < 0) return +2; // c -- a -- b がこの順番に一直線上
  if(norm(b) < norm(c)) return -2; // a -- b -- c がこの順番に一直線上
  return 0; // a -- c -- b が一直線上
}

bool is_convex(const Polygon &poly){
  for(int i = 0 ; i < (int)poly.size() ; i++){
    if(ccw(prev(poly, i), poly[i], next(poly, i)) == -1) return false;
  }
  return true;
}

int main(){
  ld x, y;
  char c;
  while(cin >> x >> c >> y >> c){
    Polygon poly;
    poly.push_back(Point(x, y));
    for(int i = 0 ; i < 2 ; i++){
      cin >> x >> c >> y >> c;
      poly.push_back(Point(x, y));
    }
    cin >> x >> c >> y;
    poly.push_back(Point(x, y));
    
    cout << (is_convex(poly) ? "YES" : "NO") << endl;
  }
  
  return 0;
}