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++: #define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<stack>
#include<cstdio>
#include<bitset>
#include<unordered_map>
#include<climits>
#include<fstream>
using namespace std;
///////////////////library zone!!!!!!!!!!!!!!!!!!!!!!!!!!!!
typedef long long ll;
typedef long double ld;
#define all(a) (a).begin(),(a).end()
#define EPS (1e-5)
const ll Mod = 1000000007;
const ll mod = 998244353;
struct H {
	ll x, y;
	bool operator<(const H &b) const {
		if (x != b.x) return x < b.x;
		return y < b.y;
	}
	bool operator>(const H &b) const {
		if (x != b.x) return x > b.x;
		return y > b.y;
	}
	bool operator==(const H &b) const { return x == b.x&&y == b.y; }
	bool operator!=(const H &b) const { return (*this) != b; }
};
struct P {
	ll pos, cost;
	bool operator<(const P &b) const { return cost < b.cost; }
	bool operator>(const P &b) const { return cost > b.cost; }
};
struct B {
	ll to, cost;
};
struct E {
	ll from, to, cost;
	bool operator<(const E &b) const { return cost < b.cost; }
	bool operator>(const E &b) const { return cost > b.cost; }
};
template<typename T, typename U>
void chmin(T &a, U b) {
	if (a > b) a = b;
}
template<typename T, typename U>
void chmax(T &a, U b) {
	if (a < b) a = b;
}
template<typename T>
T max_0(T a) {
	if (a < 0) return 0;
	return a;
}
template<typename T>
T min_0(T a) {
	if (a > 0) return 0;
	return a;
}
ll read() {
	ll u;
	ll k = scanf("%lld", &u);
	return u;
}
ll gcd(ll i, ll j) {
	if (i > j) swap(i, j);
	if (i == 0) return j;
	return gcd(j%i, i);
}
ll mod_pow(ll x, ll n, ll p) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % p;
		x = x * x % p;
		n >>= 1;
	}
	return res;
}//x^n%p
vector<string>split(string s, char c = ' ') {
	vector<string>vec;
	string h = "";
	for (int i = 0; i < s.size();) {
		int j = i;
		while (j < s.size() && s[j] != ' ') {
			h += s[j++];
		}
		if (h.size() > 0) vec.push_back(h);
h = "";
i = j + 1;
	}
	return vec;
}
template<typename T>
void print_vec(vector<T>a) {
	for (int i = 0; i < a.size(); i++) {
		cout << (i == 0 ? "" : " ") << a[i];
	}
	cout << endl;
}
const ll Inf = 3023372036854775807;
const int inf = 1500000000;
#define int long long
//----------------------------------------------------
class Vec2 {
public:
	ld x, y;
	Vec2() { x = 0, y = 0; }
	Vec2(ld x, ld y) :x(x), y(y) {}
	ld length() {
		return sqrt(x*x + y * y);
	}
	Vec2 normal() {
		ld len = this->length();
		if (len == 0) return Vec2(x, y);
		x /= len, y /= len;
		return *(this);
	}
	Vec2 operator+(Vec2 vec) {
		return Vec2(x + vec.x, y + vec.y);
	}
	Vec2 operator-(Vec2 vec) {
		return Vec2(x - vec.x, y - vec.y);
	}
	template<typename T>
	Vec2 operator*(T cons) {
		return Vec2(x*cons, y*cons);
	}
	ld operator*(Vec2 vec) {
		return x * vec.x + y * vec.y;
	}
	ld operator%(Vec2 vec) {
		return x * vec.y - y * vec.x;
	}
	bool operator==(Vec2 vec) {
		return abs(x - vec.x) < EPS && abs(y - vec.y) < EPS;
	}
};
ld dot(Vec2 a, Vec2 b) {
	return a.x*b.x + a.y*b.y;
}
ld cross(Vec2 a, Vec2 b) {
	return a.x*b.y - a.y*b.x;
}
ld areaIntegral(Vec2 a, Vec2 b) {
	return abs(a.x*b.y - a.y*b.x) / 2.0;
}
class Vec3 {
public:
	ld x, y, z;
	Vec3() { x = 0, y = 0, z = 0; }
	Vec3(ld x, ld y, ld z) :x(x), y(y), z(z) {}
	ld length() {
		return sqrt(x*x + y * y + z * z);
	}
	void normal() {
		ld len = this->length();
		if (len == 0) return;
		x /= len, y /= len, z /= len;
	}
	Vec3 operator+(Vec3 vec) {
		return Vec3(x + vec.x, y + vec.y, z + vec.z);
	}
	Vec3 operator-(Vec3 vec) {
		return Vec3(x - vec.x, y - vec.y, z - vec.z);
	}
	Vec3 operator*(int cons) {
		return Vec3(x*cons, y*cons, z*cons);
	}
	ld operator*(Vec3 vec) {
		return x * vec.x + y * vec.y + z * vec.z;
	}
};
ld dot(Vec3 a, Vec3 b) {
	return a.x*b.x + a.y*b.y + a.z*b.z;
}
class Line {
public:
	Vec2 from, to;
	Line(Vec2 from, Vec2 to) :from(from), to(to) {}
};
Line getPerpendicularBisector(Line line) {
	int cx = (line.from.x + line.to.x) / 2, cy = (line.from.y + line.to.y) / 2;
	Vec2 p = Vec2(cx + (line.from.y - line.to.y), cy + (line.to.x - line.from.x));
	return Line(Vec2(cx, cy), p);
}
signed main() {
	ld x[4], y[4];
	while (~scanf("%LF,%LF,%LF,%LF,%LF,%LF,%LF,%LF", &x[0], &y[0], &x[1], &y[1], &x[2], &y[2], &x[3], &y[3])) {
		Vec2 a = Vec2(x[0], y[0]) - Vec2(x[1], y[1]), b = Vec2(x[1], y[1]) - Vec2(x[2], y[2]), c = Vec2(x[2], y[2]) - Vec2(x[3], y[3]), d = Vec2(x[3], y[3]) - Vec2(x[0], y[0]);
		if (acos(a*-1*b / a.length() / b.length()) >= M_PI) {
			cout << "NO\n";
			continue;
		}
		if (acos(b*-1 * c / c.length() / b.length()) >= M_PI) {
			cout << "NO\n";
			continue;
		}
		if (acos(c*-1 * d / c.length() / d.length()) >= M_PI) {
			cout << "NO\n";
			continue;
		}
		if (acos(d*-1 * a / a.length() / d.length()) >= M_PI) {
			cout << "NO\n";
			continue;
		}
		ld sum = acos(d*-1 * a / a.length() / d.length()) + acos(c*-1 * d / c.length() / d.length()) +
			acos(b*-1 * c / c.length() / b.length()) + acos(a*-1 * b / a.length() / b.length());
		if (abs(sum - 2 * M_PI) < EPS) {
			cout << "YES\n";
		}
		else {
			cout << "NO\n";
		}
	}
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <vector>
#include <string>
#include <map>
#include <queue>
#include <stack>
#include <algorithm>

#define rep(i,j) REP((i), 0, (j))
#define REP(i,j,k) for(int i=(j);(i)<(k);++i)
#define between(a,x,b) ((a)<=(x)&&(x)<=(b))
using namespace std;

typedef struct POINT_tag{ double x, y;}POINT_t;
typedef struct LINE_tag{ POINT_t a, b;}LINE_t;

int side(POINT_t *p, LINE_t *e){
  POINT_t p1 = *p;
  POINT_t p2 = e->a;
  POINT_t p3 = e->b;

  const int n = p1.x * (p2.y - p3.y) + p2.x * (p3.y - p1.y) + p3.x * (p1.y - p2.y);
  if (n > 0) return 1;
  else if(n < 0) return -1;
  else return 0;
}

int main(){
  POINT_t a, b, c, d;
  while(scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf,%lf",&a.x,&a.y,&b.x,&b.y,&c.x,&c.y,&d.x,&d.y) != EOF){
    LINE_t ac, bd;
    ac.a = a; ac.b = c;
    bd.a = b; bd.b = d;
    if(side(&a, &bd) != side(&c, &bd) && side(&b, &ac) != side(&d, &ac)) puts("YES");
    else puts("NO");
  }
  return 0;
}