#include <iostream>
#include <cmath>
#include <vector>

using namespace std;

float calc_crossProduct(float x1, float y1, float x2, float y2){
  return (x1*y2-y1*x2);
}

int main(){
  int cnt = 0;
  while(true){
    string strall;
    cin >> strall;
    
    vector<float> x(4, 0.0);
    vector<float> y(4, 0.0);
    char c;
    for(int i=0;i<4;i++){
      int pos = strall.find(",");
      //      cout << pos << endl;
      //      cout << strall.substr(0, pos) << endl;
      x[i] = std::stof(strall.substr(0, pos));
      
      strall.erase(strall.begin(), strall.begin() +  pos + 1);
      //      cout << strall << endl;
      
      //      cout << strall.substr(0, pos) << endl; 
      y[i] = std::stof(strall.substr(0, pos));
      strall.erase(strall.begin(), strall.begin() + pos + 1);
    }

    if(cnt < 2){
      for(int i=0;i<4;i++){
	//	cout << "(" << x[i] << ", " << y[i] << ")" << endl;
      }
      cnt++;
    }


    bool flag = true;
    vector<float> cp(4, 0.0);    
    for(int i=0;i<4;i++){
     
      float x1 = x[i];float y1 = y[i];
      float x2 = x[(i+1)%4];float y2 = y[(i+1)%4];
      float x3 = x[(i+2)%4];float y3 = y[(i+2)%4];

      float x2x1 = x2-x1; float y2y1 = y2-y1;
      float x3x1 = x3-x1; float y3y1 = y3-y1;

      cp[i] = calc_crossProduct(x2x1, y2y1, x3x1, y3y1);
      if(cp[i] < 0){
	flag = false;
	break;
      }
    }

    if(flag != false){
      cout << "YES" << endl;
    }else{
      cout << "NO" << endl;
    }
  }  
}

  

    




  

  
  