Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"fmt"
)

func check(x, y, x1, y1, x2, y2 float64) float64 {
	return (x2-x1)*y - (y2-y1)*x + x1*y2 - x2*y1
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	a := make([]float64, 8)
	for scanner.Scan() {
		info := strings.Split(scanner.Text(), ",")
		for j := 0; j < 8; j++ {
			a[j], _ = strconv.ParseFloat(info[j], 64)
		}
		if check(a[0], a[1], a[2],a[3], a[6], a[7])*check(a[4], a[5], a[2], a[3], a[6], a[7]) < 0 && check(a[6], a[7], a[0], a[1], a[4], a[5])*check(a[2],a[3], a[0], a[1], a[4], a[5]) < 0 {
			fmt.Println("YES")	
		} else {
			fmt.Println("NO")
		}
	}
}

C++: #include<iostream>
#include<cfloat>
#include<cassert>
#include<cmath>
#include<vector>
#include<algorithm>
#include<stdio.h>
using namespace std;
 
#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS )
#define dle(a, b) (equals(a, b) || a < b )
static const double PI = acos(-1);

class Point{
public:
  double x, y;
  
  Point ( double x = 0, double y = 0): x(x), y(y){}
  
  Point operator + ( Point p ){ return Point(x + p.x, y + p.y); }
  Point operator - ( Point p ){ return Point(x - p.x, y - p.y); }
  Point operator * ( double a ){ return Point(x*a, y*a); }
  Point operator / ( double a ){ return Point(x/a, y/a); }
  
  double abs() { return sqrt(norm());}
  double norm() { return x*x + y*y; }
  
  bool operator < ( const Point &p ) const {
    return x != p.x ? x < p.x : y < p.y;
  }
  
  bool operator == ( const Point &p ) const {
    return fabs(x-p.x) < EPS && fabs(y-p.y) < EPS;
  }
};

class Segment{
public:
  Point p1, p2;
  Segment ( Point p1 = Point(0.0,0.0), Point p2 = Point(0.0,0.0)): p1(p1), p2(p2){}
  double abs() { return sqrt(norm());}
  double norm() { return (p2.x - p1.x)*(p2.x - p1.x) + (p2.y - p1.y)*(p2.y - p1.y); }
};
typedef Segment Line;
typedef Point Vector;
typedef vector<Point> Polygon;
double norm( Vector a ){ return a.x*a.x + a.y*a.y; }
double abs( Vector a ){ return sqrt(norm(a)); }
Point polar( double a, double r ){ return Point(cos(r)*a, sin(r)*a);}
double getDistance( Vector a, Vector b ){ return abs(a - b); }
double dot( Vector a, Vector b ){ return a.x*b.x + a.y*b.y; }
double cross( Vector a, Vector b ){ return a.x*b.y - a.y*b.x; }
bool isOrthogonal( Vector a, Vector b){
  return equals(dot(a,b),0.0);
}
bool isOrthogonal(Segment s1,Segment s2){
  return equals( dot(s1.p2-s1.p1 , s2.p2-s2.p1) ,0.0 );
}
bool isParallel(Vector a, Vector b){
  return equals(cross(a,b),0.0);
}
bool isParallel(Point a1,Point a2,Point b1,Point b2){
  return isParallel(a1-a2,b1-b2);
}
bool isParallel(Segment s1,Segment s2){
  return equals(cross(s1.p2 - s1.p1 , s2.p2 - s2.p1),0.0);
}
Point project(Segment s,Point p){
  Vector base = s.p2-s.p1;
  double t = dot(p-s.p1,base)/norm(base);
  return s.p1+base*t;
}
Point reflect(Segment s,Point p){
  return p + (project(s,p)-p)*2.0;
}

static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;
 
// EPS can be 0
// need to check for 920, 833, 866
int ccw( Point p0, Point p1, Point p2 ){
    Vector a = p1 - p0;
    Vector b = p2 - p0;
    if ( cross(a, b) > EPS ) return COUNTER_CLOCKWISE;
    if ( cross(a, b) < -EPS ) return CLOCKWISE;
    if ( dot(a, b) < -EPS ) return ONLINE_BACK;
    if ( norm(a) < norm(b) ) return ONLINE_FRONT;
    return ON_SEGMENT;
}

bool isIntersect(Point p1, Point p2,Point p3,Point p4){
  return (ccw(p1,p2,p3) * ccw(p1,p2,p4) <=0 &&
	  ccw(p3,p4,p1) * ccw(p3,p4,p2) <=0);
}

bool isIntersect(Segment s1,Segment s2){
  return isIntersect(s1.p1 , s1.p2 , s2.p1 , s2.p2);
}

Point getCrossPoint(Segment s1,Segment s2){
  assert(isIntersect(s1,s2));
  Vector base = s2.p2 - s2.p1;
  double d1 = abs(cross(base, s1.p1-s2.p1));
  double d2 = abs(cross(base, s1.p1-s2.p1));
  double t = d1/(d1+d2);
  return s1.p1 + (s1.p2 - s1.p1)*t;
}

double getDistanceLP(Line s,Point p){
  return abs(cross(s.p2-s.p1,p-s.p1)/abs(s.p2-s.p1));
}

double getDistanceSP(Segment s,Point p){
  if(dot(s.p2-s.p1,p-s.p1)<0.0)return abs(p-s.p1);
  if(dot(s.p1-s.p2,p-s.p2)<0.0)return abs(p-s.p2);
  return getDistanceLP(s,p);
}

double getDistance(Segment s1,Segment s2){
  if(isIntersect(s1,s2))return 0.0;
  return min(min(getDistanceSP(s1,s2.p1),getDistanceSP(s1,s2.p2)),
	     min(getDistanceSP(s2,s1.p1),getDistanceSP(s2,s1.p2)));
}

bool isConvex( Point P[4] ){
    int c = ccw(P[0], P[1], P[2]);
    for ( int i = 1; i < 4; i++ ){
      if ( c != ccw(P[i], P[(i+1)%4], P[(i+2)%4] )) return false;
    }
    return true;
}
bool isConvex( vector<Point> P ){
    int c = ccw(P[0], P[1], P[2]);
    for ( int i = 1; i < 4; i++ ){
      if ( c != ccw(P[i], P[(i+1)%4], P[(i+2)%4] )) return false;
    }
    return true;
}

Polygon andrewScan(Polygon s){
  Polygon u,l;
  if(s.size()<3)return s;
  sort(s.begin(),s.end());
  u.push_back(s[0]);
  u.push_back(s[1]);
  l.push_back(s[s.size()-1]);
  l.push_back(s[s.size()-2]);
  
  //int n;
  for(int i=2;i<(int)s.size();i++){
    for(int n=u.size();n>=2&&ccw(u[n-2],u[n-1],s[i])!=CLOCKWISE;n--){
      u.pop_back();
    }
    u.push_back(s[i]);
  }
  
  for(int i=s.size()-3;i>=0;i--){
    for(int n=l.size();n>=2&&ccw(l[n-2],l[n-1],s[i])!=CLOCKWISE;n--){
      l.pop_back();
    }
    l.push_back(s[i]);
  }
  
  reverse(l.begin(),l.end());
  for(int i=u.size()-2;i>=1;i--)l.push_back(u[i]);
  
  return l;
}


Point in[4];

bool check(Polygon a){
  if(a.size()!=4)return false;
  int i,j;
  for(i=0;i<4;i++){
    //cout<<a[i].x<<" "<<a[i].y<<endl;
    for(j=0;j<4;j++){
      if(in[(j+i)%4]==a[j]){

      }else{
	break;
      }
    }
    if(j==4)return true;
  }
  return false;
}


int main(){
  char ch;


  while(cin>>in[0].x>>ch>>in[0].y>>ch>>in[1].x>>ch>>in[1].y>>ch>>in[2].x>>ch>>in[2].y>>ch>>in[3].x>>ch>>in[3].y){
    
    vector<Point> t,u;
    for(int i=0;i<4;i++){
      t.push_back(in[i]);
    }
    //cout<<t.size()<<endl;
    u=andrewScan(t);
    //cout<<u.size()<<endl;
    cout<<(check(u)==true?"YES":"NO")<<endl;

    //cout<<"a"<<endl;
  }

  return 0;
}

C++: #include<iostream>
#include<string>
#include<sstream>
#include<algorithm>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<stack>
#include<queue>
#include<deque>
using namespace std;

bool sameside (double ax, double ay, double bx, double by, double cx, double cy, double dx, double dy) {
    bool result = false;
    if (ax != bx) {
        double r = (ay - by) / (ax - bx);
        double s = ay - r * ax;
        if ( (r * cx + s - cy) * (r * dx + s - dy) > 0) {
            result = true;
        }
    } else {
        if ( (cx - ax) * (dx - ax) > 0 ) {
            result = true;
        }
    }
    return result;
}

int main() {
     
    double ax, ay, bx, by, cx, cy, dx, dy;
    char c;
    while(cin >> ax >> c >> ay >> c >> bx >> c >> by >> c >> cx >> c >> cy >> c >> dx >> c >> dy) {
        if( sameside(ax, ay, cx, cy, bx, by, dx, dy) || sameside(bx, by, dx, dy, ax, ay, cx, cy) ) {
            cout << "NO" << endl;
        } else {
            cout << "YES" << endl;
        }
    }
    return 0;
}