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 <queue>
#include <stack>
#include <vector>
#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <string>
#include <cmath>
using namespace std;

#define rep(i,n) for(int i=0;i<int(n);++i)
static const double PI=6*asin(0.5);

double x[5],y[5];
char tmp;
double h[5];
double ang[4];//0:bac 1:bca 2:acd 3:cad

int main(){
	while(cin>>x[0]>>tmp>>y[0]){
		rep(i,3){
			cin>>tmp>>x[i+1]>>tmp>>y[i+1];
		}
		x[4] = x[0]; y[4] = y[0];
		rep(i,4){
			double X = x[i+1]-x[i],Y = y[i+1]-y[i];
			h[i] = sqrt(X*X+Y*Y);
			//cout << "h["<<i<<"] = "<<h[i]<<endl;
		}
		//cout<<acos(0.5)<<endl;
		h[4] = sqrt((x[2]-x[0])*(x[2]-x[0])+(y[2]-y[0])*(y[2]-y[0]));
		ang[0] = acos((h[0]*h[0]+h[4]*h[4]-h[1]*h[1])/(2*h[0]*h[4]));
		ang[1] = acos((h[1]*h[1]+h[4]*h[4]-h[0]*h[0])/(2*h[1]*h[4]));
		ang[2] = acos((h[2]*h[2]+h[4]*h[4]-h[3]*h[3])/(2*h[2]*h[4]));
		ang[3] = acos((h[3]*h[3]+h[4]*h[4]-h[2]*h[2])/(2*h[3]*h[4]));
		//cout << (h[0]*h[0]+h[4]*h[4]-h[1]*h[1])/(2*h[0]*h[4])<<endl;
		//rep(i,4) cout<<ang[i]<<endl;
		if(PI>(ang[0]+ang[3])&&PI>ang[1]+ang[2]){
			cout<<"YES\n";
		}
		else{
			cout<<"NO\n";
		}
	}
	return 0;
}

C++: #include <iostream>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <tuple>
#include <queue>
#include <set>
#include <cstdio>
#include <climits>
#include <cmath>
#include <array>
#include <functional>
#include <sstream>
#include <list>
#include <iomanip>
#include <set>
const int MOD=1000000007;
const int INF=1000000000;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
const double eps=1e-10;
const int inf=1e9;
typedef pair<int,int> P;
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;

class Point
{
public:
  double x,y;
  Point(double x,double y): x(x),y(y){}
  Point operator + (const Point &p)
  {
    return Point(x+p.x,y+p.y);
  }
  Point operator - (const Point &p)
  {
    return Point(x-p.x,y-p.y);
  }
  Point operator * (double k)
  {
    return Point(x*k,y*k);
  }
  Point operator / (double k)
  {
    return Point(x/k,y/k);
  }
  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;
  }
  double abs(){return sqrt(norm());}
  double norm(){return x*x+y*y;}
};
typedef Point Vector;
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;
}
double norm(Point a)
{
  return a.x*a.x + a.y*a.y;
}
double abs(Vector a)
{
  return sqrt(norm(a));
}
struct Segment
{
  Point p1,p2;
  Segment(Point p1,Point p2): p1(p1),p2(p2){}
};
typedef Segment Line;

class Circle
{
public:
  Point c;
  double r;
  Circle(Point c,double r):  c(c),r(r){}
};

typedef vector<Point> Polygon;


bool isorthogonal(Vector a,Vector b)
{
  return fabs(dot(a,b)-0.0)<eps;
}

bool isparallel(Vector a,Vector b)
{
  return fabs(cross(a,b)-0.0)<eps;
}
Point project(Segment s,Point p)
{
  Vector base=s.p2-s.p1;
  double r=dot(p-s.p1,base) / norm(base);
  return  s.p1 + base*r;
}
Point reflect(Segment s,Point p)
{
  return p+ (project(s,p)-p)*2.0;
}
double getdistance(Point a,Point b)
{
  return abs(a-b);
}
double getdistanceLP(Line l,Point p)
{
  return abs(cross(l.p2-l.p1,p-l.p1) / abs(l.p2-l.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);
}

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(a.norm()<b.norm()) return ONLINE_FRONT;
  return ON_SEGMENT;
}
bool intersect(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 intersect(Segment s1,Segment s2)
{
  return intersect(s1.p1,s1.p2,s2.p1,s2.p2);
}
Point getcrosspoint(Segment s1,Segment s2)
{
  Vector base =s2.p2-s2.p1;
  double d1=abs(cross(base,s1.p1-s2.p1));
  double d2=abs(cross(base,s1.p2-s2.p1));
  double t=d1/(d1+d2);
  return s1.p1+(s1.p2-s1.p1)*t;
}

double getdistanceSS(Segment s1,Segment s2)
{
  if(intersect(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)));
}

pair<Point,Point> getcrosspoints(Circle c,Line l)
{
  //assert(intersect(c,l));
  Vector pr=project(l,c.c);
  Vector e=(l.p2-l.p1)/abs(l.p2-l.p1);
  double base=sqrt(c.r*c.r - norm(pr-c.c));
  return make_pair(pr+e*base,pr-e*base);
}

double arg(Vector p){return atan2(p.y,p.x);}
Vector polar(double a,double r){return Point(cos(r)*a,sin(r)*a);}
pair <Point,Point> getcrosspoints(Circle c1,Circle c2)
{
  double d=abs(c1.c-c2.c);
  double a=acos((c1.r*c1.r+d*d-c2.r*c2.r) / (2*c1.r*d));
  double t=arg(c2.c-c1.c);
  return make_pair(c1.c+polar(c1.r,t+a),c1.c+polar(c1.r,t-a));
}
int contains(Polygon g,Point p)
{
  int n=g.size();
  bool x=false;
  for(int i=0;i<n;i++)
    {
      Point a=g[i]-p,b=g[(i+1)%n]-p;
      if(abs(cross(a,b)) < eps && dot(a,b)<eps) return 1;
      if(a.y>b.y) swap(a,b);
      if(a.y <eps && eps<b.y && cross(a,b)>eps) x=!x;
    }
  return (x ? 2 : 0);
}

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]);
  for(int i=2;i<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;
}
int main(int argc,char const* argv[])
{
  int n;
  double ax,ay,bx,by,cx,cy,dx,dy;
  char ch;
  while(cin >> ax >>ch >> ay >>ch>> bx >>ch>> by >>ch>> cx >>ch>> cy >>ch>> dx >>ch>>  dy)
    {
      Point a=Point(ax,ay);
      Point b=Point(bx,by);
      Point c=Point(cx,cy);
      Point d=Point(dx,dy);
      if(ccw(a,b,c)==ccw(b,c,d) && ccw(b,c,d)==ccw(c,d,a) && ccw(c,d,a)==ccw(a,b,c))
	{
	  cout << "YES" <<endl;
	}
      else
	{
	  cout << "NO" << endl;
	}
    }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
using namespace std;

class Point {
public:
    double x, y;
};

bool isIntersect(Point p1, Point p2, Point p3, Point p4) {
    return ((p1.x - p2.x) * (p3.y - p1.y) + (p1.y - p2.y) * (p1.x - p3.x))
        * ((p1.x - p2.x) * (p4.y - p1.y) + (p1.y - p2.y) * (p1.x - p4.x)) < 0;
}

int main () {
    Point p[4];
    while (scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",
                 &p[0].x, &p[0].y, &p[1].x, &p[1].y, &p[2].x, &p[2].y, &p[3].x, &p[3].y) != EOF) {
        if (isIntersect(p[0], p[2], p[1], p[3]) && isIntersect(p[1], p[3], p[0], p[2])) {
            cout << "YES" << endl;
        } else {
            cout << "NO" << endl;
        }
    }
}