#include <iostream>
#include <cstdio>

class Point{
public:
	Point();
	Point(double _x, double _y);
	double x, y;
};

Point::Point() : x(0), y(0){}
Point::Point(double _x, double _y) : x(_x), y(_y){}

class Vector{
	//private:

public:
	Vector();
	Vector(double _x, double _y);
	Vector(Point p1, Point p2);
	double x, y;
};

Vector::Vector() : x(0), y(0){}
Vector::Vector(double _x, double _y) : x(_x), y(_y){}
Vector::Vector(Point p1, Point p2) : x(p1.x-p2.x), y(p1.y-p2.y){}

class Triangle{
public:
	Triangle();
	Triangle(Point _p1, Point _p2, Point _p3);
	Point p[3];
};

Triangle::Triangle(Point _p1, Point _p2, Point _p3){
	p[0] = _p1, p[1] = _p2, p[2] = _p3;
}

int extproduct(Vector v1, Vector v2){
	return v1.x*v2.y - v1.y*v2.x;
}

bool triangle_contains(Triangle t, Point p){
	int count = 0;
	for(int i=0;i<3;i++){
		Vector a = Vector(t.p[i], t.p[(i+1)%3]), b = Vector(p, t.p[i]);
		if(extproduct(a, b) > 0)count++;
		else count--;
	}
	return (count%3 != 0);
}

int main(){
	Point ps[4];
	while(~scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf", &ps[0].x, &ps[0].y, &ps[1].x, &ps[1].y, &ps[2].x, &ps[2].y, &ps[3].x, &ps[3].y)){
		int i = 0;
		for(;i<4;i++){
			if(triangle_contains(Triangle(ps[(i+1)%4], ps[(i+2)%4], ps[(i+3)%4]), ps[i]) == false)break;
		}
		if(i == 4)puts("YES");
		else puts("NO");
	}
}