#include <bits/stdc++.h>

#define PI 3.14159265358979

using namespace std;

int main()
{
	string str;
	while(cin >> str)
	{
		double x[4],y[4];
		string keep;
		vector<string>set;
		int flag=0;
		double a[4];
		double s[4];
		int j=0;

		for(int i=0;i<=str.length();i++)
		{
			if(str[i]==',' || str.length()==i)
			{
				set.push_back(keep);
				keep.clear();
			}
			else keep+=str[i];
		}

		stringstream ss;
		for(int i=0,j=0;i<4;i++,j+=2)
		{
			ss << set[j];
			ss >> x[i];

			ss.clear();
			ss.str("");

			ss << set[j+1];
			ss >> y[i];

			ss.clear();
			ss.str("");
		}

		for(int i=0;i<4;i++)
		{
			if(x[(i+1)%4]-x[i]!=0)a[i]=(y[(i+1)%4]-y[i])/(x[(i+1)%4]-x[i]);
			else a[i]=9999999;
		}

		double sum=0;
		for(int i=0;i<4;i++)
		{
			double set[100]={};

			set[0]=fabs(a[i]*a[(i+1)%4]+1);
			set[1]=sqrt(a[i]*a[i]+1);
			set[2]=sqrt(a[(i+1)%4]*a[(i+1)%4]+1);

			if(set[1]*set[2]==0)s[i]=90;
			else s[i]=acos(set[0]/(set[1]*set[2]))*180/PI;

			sum+=s[i];
		}
		if(fabs(360-sum)>=179.9999)cout << "NO" << endl;
		else cout << "YES" << endl;
	}


	return 0;
}