#include <cstdio>
#include <algorithm>
using namespace std;

class Point {
  public:
    int x, y;
    bool operator < (const Point& other) const;
};
int cross_product(Point o, Point a, Point b) { return (a.x - o.x) * (b.y - o.y) - (a.y - o.y) * (b.x - o.x); }
bool Point::operator < (const Point& other) const { return x == other.x ? y < other.y : x < other.x; }

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

vector<Point> _alg(vector<Point> points) {
  vector<Point> res;
  int sz = 0;
  for(Point p : points) {
    while(sz > 1 && cross_product(res[sz-2], res[sz-1], p) <= 0) {
      res.pop_back();
      sz -= 1;
    }
    res.push_back(p);
    sz += 1;
  }
  return res;
}

vector<Point> convex_hull(vector<Point> points) {
  sort(points.begin(), points.end());
  if(points.size() <= 1) { return points; }
  vector<Point> lower = _alg(points);
  reverse(points.begin(), points.end());
  vector<Point> upper = _alg(points);
  vector<Point> res;
  for(int i : range(lower.size()-1)) { res.push_back(lower[i]); }
  for(int i : range(upper.size()-1)) { res.push_back(upper[i]); }
  return res;
}

int main(void) {
  vector<Point> points(5);
  for(int i : range(5)) {
    Point p;
    scanf("%d%d", &p.x, &p.y);
    points[i] = p;
  }
  int res = convex_hull(points).size();
  puts(res == 5 ? "YES" : "NO");
  return 0;
}