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<bits/stdc++.h>
using namespace std;

/* 平面幾何の基本要素 */
 
#define EPS (1e-10)
#define equals(a,b) (fabs((a) - (b)) < EPS )
 
class Point { // 点を表すクラス
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(a * x, a * y); }
  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;
  }
};

typedef Point Vector; // ベクトルを表す構造体

struct Segment { // 線分を表す構造体
  Point p1,p2;
};

typedef Segment Line; // 直線を表す構造体

class Circle { // 円を表すクラス
public:
  Point c;
  double r;
  Circle(Point c = Point(), double r = 0.0): c(c),r(r) {}
};
typedef vector < Point > Polygon; // 多角形

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;
}

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;
 
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,s2.p1,s1.p2,s2.p2);
}

int main(){
  Point p1,p2,p3,p4;
  char o;
  while(cin >> p1.x >> o >> p1.y >> o >> p2.x >> o >> p2.y >> o >> p3.x >> o >> p3.y >> o >> p4.x >> o >> p4.y){
    Segment s1,s2;
    s1.p1 = p1;
    s1.p2 = p2;
    s2.p1 = p3;
    s2.p2 = p4;
    if(intersect(s1,s2)) cout << "YES" << endl;
    else cout << "NO" << endl;
  }
}