#include <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>
#include <functional>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = { -1, 0, 1, 0 }; const int dy[] = { 0, 1, 0, -1 };

int main() {
	double point[8];
	
	char c;
	bool yes;
	while (cin >> point[0] >> c >> point[1] >> c >> point[2] >> c >> point[3] >> c >> point[4] >> c >> point[5] >> c >> point[6] >> c >> point[7]){
		vector<bool> posi;
		yes=true;
		REP(i, 4){
			double angle = point[i * 2] * point[(i * 2 + 2) % 8 + 1] - point[i * 2 + 1] * point[(i * 2 + 2) % 8];
			if (angle>0.0){
				posi.push_back(true);
			} else if(angle<0.0) {
				posi.push_back(false);
			}
		}
		if (posi[0] == posi[1] && posi[2] == posi[1] && posi[2] == posi[3])
			cout << "YES"<<endl;
			else
				cout << "NO" << endl;
	}
	return 0;
}