#include<iostream>
#include<complex>
#include<stdio.h>
#include<math.h>
using namespace std;
typedef struct point{
	double x,y;
} point;
point vect(point a,point b){
	point l;
	l.x = a.x -b.x;
	l.y = a.y -b.y;
	return l;
}

double cos(point a,point b, point c){
	point p1,p2; double inner;
	p1 = vect(a,c);
	p2 = vect(b,c);
	inner = p1.x * p2.x + p1.y*p2.y;
	return inner;

}

int main(){
	char a;
	double l[4];
	while(1){
	bool ans = true;
	point p[4]; 
		for(int i=0;i<4;i++)
	if(scanf("%lf,%lf,",&p[i].x,&p[i].y) == EOF) return 0;
	
    if(cos(p[3],p[1],p[0]) < 0) ans = false;
	if(cos(p[0],p[2],p[1]) < 0) ans = false;
	if(cos(p[3],p[1],p[2]) < 0) ans = false;
	if(cos(p[2],p[0],p[3]) < 0) ans = false;
	
	if(ans == true) {cout << "YES" << endl;} else {cout << "NO" << endl; }
}


}