#include <bits/stdc++.h>
using namespace std;
#include "../..//library/unfinished/convex_hull.cpp"

#define fs first
#define sc second
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define pb emplace_back

using pii = pair<int, int>;
using vi = vector<int>;
using lint = long long;

const int inf = 1001001001;
const lint linf = 1001001001001001001ll;
const int mod = 1e9 + 7;
const int dx[]{0, 1, 0, -1, -1, -1, 1, 1}, dy[]{1, 0, -1, 0, -1, 1, -1, 1};

template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; } return a > b; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; } return a < b; }
template<typename T> inline void print(const T &x, string s = "\n") { cout << x << s; }
template<typename T> inline void print(const vector<T> &v, string s = " ") 
{ rep(i, v.size()) cout << v[i] << (i + 1 == v.size() ? "\n" : s); }
inline bool inside(int y, int x, int H, int W) { return 0 <= y && y < H && 0 <= x && x < W; }
inline lint in() { lint x; std::cin>>x; return x; }

int main() {
	double a, b;
	char c;
	vector<Point> vi;
	while (cin >> a >> c >> b) {
		vi.clear();
		vi.pb(Point(a, b));
		rep(i, 3) {
			cin >> c >> a >> c >> b;
			vi.pb(Point(a, b));
		}

		vector<Point> po = convex_hull(vi, vi.size());
		cout << (po.size() == vi.size() ? "YES" : "NO") << endl;
	}
}