#include <bits/stdc++.h>

using namespace std;

namespace arithmetic {
  template<typename T> class Addition {
  public:
    template<typename V> T operator+(const V& v) const {
      return T(static_cast<const T&>(*this)) += v;
    }
  };

  template<typename T> class Subtraction {
  public:
    template<typename V> T operator-(const V& v) const {
      return T(static_cast<const T&>(*this)) -= v;
    }
  };

  template<typename T> class Multiplication {
  public:
    template<typename V> T operator*(const V& v) const {
      return T(static_cast<const T&>(*this)) *= v;
    }
  };

  template<typename T> class Division {
  public:
    template<typename V> T operator/(const V& v) const {
      return T(static_cast<const T&>(*this)) /= v;
    }
  };

  template<typename T> class Modulus {
  public:
    template<typename V> T operator%(const V& v) const {
      return T(static_cast<const T&>(*this)) %= v;
    }
  };
}

template<typename T> class IndivisibleArithmetic : public arithmetic::Addition<T>, public arithmetic::Subtraction<T>, public arithmetic::Multiplication<T> {};

template<typename T> class Arithmetic : public IndivisibleArithmetic<T>, public arithmetic::Division<T> {};

template<typename T> class Ordered {
public:
  template<typename V> bool operator==(const V& v) const {
    return !(static_cast<T>(v) < static_cast<const T&>(*this) || static_cast<const T&>(*this) < static_cast<T>(v));
  }
  
  template<typename V> bool operator!=(const V& v) const {
    return static_cast<T>(v) < static_cast<const T&>(*this) || static_cast<const T&>(*this) < static_cast<T>(v);
  }

  template<typename V> bool operator>(const V& v) const {
    return static_cast<T>(v) < static_cast<const T&>(*this);
  }

  template<typename V> bool operator<=(const V& v) const {
    return !(static_cast<T>(v) < static_cast<const T&>(*this));
  }

  template<typename V> bool operator>=(const V& v) const {
    return !(static_cast<const T&>(*this) < static_cast<T>(v));
  }
};

template<typename T> inline T gcd(T a, T b) {
  return __gcd(a, b);
}

template<typename T> inline T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}

template<typename T> inline T floor(T a, T b) {
  return floor(a / b) * b <= a ? floor(a / b) : floor(a / b) - 1;
}

template<typename T> inline T ceil(T a, T b) {
  return floor(a + b - 1, b);
}

template<typename T> inline T round(T a, T b) {
  return floor(a + b / 2);
}

template<typename T> inline T mod(T a, T b) {
  return a - floor(a, b) * b;
}

template<typename T> inline T factorial(T n) {
  return n <= 1 ? 1 : factorial(n - 1) * n;
}

template<typename T> inline T square(T n) {
  return n * n;
}

template<typename T> inline T cube(T n) {
  return n * n * n;
}

template<typename T> inline T norm(T x1, T y1, T x2, T y2) {
  return square(x1 - x2) + square(y1 - y2);
}

inline long long sqrt(long long n) {
  return sqrt((long double)n);
}

class Real : public Arithmetic<Real>, public arithmetic::Modulus<Real>, public Ordered<Real> {
private:
  long double val;

  operator long double() const {return val;}

public:
  static long double EPS;
  static int precision;

  Real() {}

  Real(long double val) : val(val) {}

  Real operator-() const {return -val;}

  template<typename T> Real operator+=(const T& r) {
    val += static_cast<long double>(r);
    return *this;
  }

  template<typename T> Real operator-=(const T& r) {
    val -= static_cast<long double>(r);
    return *this;
  }

  template<typename T> Real operator*=(const T& r) {
    val *= static_cast<long double>(r);
    return *this;
  }

  template<typename T> Real operator/=(const T& r) {
    val /= static_cast<long double>(r);
    return *this;
  }

  template<typename T> Real operator%=(const T& r) {return *this = mod(*this, static_cast<Real>(r));}

  template<typename T> Real operator-(const T& v) const {return Real(*this) -= v;}

  template<typename T> Real operator*(const T& v) const {return Real(*this) *= v;}

  template<typename T> Real operator/(const T& v) const {return Real(*this) /= v;}

  template<typename T> bool operator<(const T r) const {return val < static_cast<long double>(r) - EPS;}

  Real abs() const {return std::abs(val);}

  Real sqrt() const {return std::sqrt(val);}

  long double toLongDouble() const {return val;}
};

long double Real::EPS = 1e-10;
int Real::precision = 15;

inline ostream& operator<<(ostream& os, const Real& a) {
  os << fixed << setprecision(Real::precision) << a.toLongDouble();
  return os;
}

inline istream& operator>>(istream& is, Real& a) {
  long double n;
  is >> n;
  a = n;
  return is;
}

Real floor(const Real& r) {
  return floor(r.toLongDouble());
}

class Point : public Arithmetic<Point>, public Ordered<Point> {
public:
  Real x, y;

  Point() {}

  Point(const Real& x) : x(x), y(0) {}

  Point(const Real& x, const Real& y) : x(x), y(y) {}

  Point operator+=(const Point& p) {
    x += p.x;
    y += p.y;
    return *this;
  }

  Point operator-=(const Point& p) {
    x -= p.x;
    y -= p.y;
    return *this;
  }

  Point operator*=(const Point& p) {
    Real xx = x * p.x - y * p.y;
    y = x * p.y + y * p.x;
    x = xx;
    return *this;
  }

  Point operator*=(const Real& r) {
    x *= r;
    y *= r;
    return *this;
  }

  Point operator/=(const Point& p) {
    Real nrm = p.norm();
    Real xx = (x * p.x + y * p.y) / nrm;
    y = (y * p.x - x * p.y) / nrm;
    x = xx;
    return *this;
  }

  Point operator/=(const Real& r) {
    x /= r;
    y /= r;
    return *this;
  }

  bool operator<(const Point& p) const {
    return (x == p.x) ? y < p.y : x < p.x;
  }

  Real norm() const {
    return x * x + y * y;
  }

  Real abs() const {
    return norm().sqrt();
  }

  Point conj() const {
    return Point(x, -y);
  }
};

inline Point operator*(const Real& real, const Point& point) {return point * real;}

inline Point operator/(const Real& real, const Point& point) {return point / real;}

inline ostream& operator<<(ostream& os, const Point& point) {
  os << point.x << " " << point.y;
  return os;
}

inline istream& operator>>(istream& is, Point& point) {
  Real x, y;
  is >> x >> y;
  point = Point(x, y);
  return is;
}

class Line {
public:
  Point a, b;

  Line() {}

  Line (const Point& a, const Point& b) : a(a), b(b) {}

  bool operator==(const Line& line) const {
    return ((line.vec() / vec()).y == 0) && (((line.a - a) / vec()).y == 0);
  }

  Point vec() const {
    return b - a;
  }
};

inline ostream& operator<<(ostream& os, const Line& line) {
  os << line.a << " " << line.b;
  return os;
}

inline istream& operator>>(istream& is, Line& line) {
  Point a, b;
  is >> a >> b;
  line = Line(a, b);
  return is;
}

class Segment : public Line, public Ordered<Segment> {
public:
  Segment() {}

  Segment (const Point& a, const Point& b) : Line(a, b) {}

  bool operator<(const Segment& segment) const {
    return a == segment.a ? b < segment.b : a < segment.a;
  }
};

enum CCW{LEFT = 1, RIGHT = 2, BACK = 4, FRONT = 8, ON = 16};

int ccw(const Point& a, const Point& b, const Point& c) {
  Point p = (c - a) / (b - a);
  if (p.y > 0) return LEFT;
  if (p.y < 0) return RIGHT;
  if (p.x < 0) return BACK;
  if (p.x > 1) return FRONT;
  return ON;
}

int ccw(const Segment& segment, const Point& point) {
  return ccw(segment.a, segment.b, point);
}

int ccw(const Line& line, const Point& point) {
  int res = ccw(line.a, line.b, point);
  if (res == BACK || res == FRONT) res = ON;
  return res;
}

class Polygon : public vector<Point> {
public:
  Polygon() {}

  Polygon(int n) : vector<Point>(n) {}

  Polygon(const initializer_list<Point>& p) : vector<Point>(p) {}

  Polygon(const vector<Point>& p) : vector<Point>(p) {}

  vector<Segment> getSides() const {
    if (size() <= 1u) return {};
    vector<Segment> res;
    Point pre = back();
    for (const auto& point : *this) {
      res.emplace_back(pre, point);
      pre = point;
    }
    return res;
  }

  vector<array<Point, 3>> getCorners() const {
    if (size() <= 2u) return {};
    vector<array<Point, 3>> res;
    Point pre1 = *(end() - 2), pre2 = back();
    for (const auto& point : *this) {
      res.emplace_back(array<Point,3>({{pre1, pre2, point}}));
      pre1 = pre2;
      pre2 = point;
    }
    return res;
  }

  Point& operator[](int i) {
    return vector::operator[](mod(i, (int)size()));
  }

  const Point& operator[](int i) const {
    return vector::operator[](mod(i, (int)size()));
  }

  template<bool strict = false> bool cover(const Point& point) const {
    bool res = false;
    for (auto& side : getSides()) {
      if (ccw(side, point) == ON) return strict ? false : true;
      if (side.a.y > side.b.y) std::swap(side.a, side.b);
      if (side.a.y <= point.y && point.y < side.b.y && ((side.b - point) / (side.a - point)).y > 0) res = !res;
    }
    return res;
  }
};

inline Real area(const Segment& segment) {
  return (segment.a.x * segment.b.y - segment.a.y * segment.b.x) / 2;
}

inline Real area(const Polygon& polygon) {
  auto side = polygon.getSides();
  auto f = [](const Real& r, const Segment& segment){return r + area(segment);};
  return accumulate(side.begin(), side.end(), Real(0), f);
}

vector<string> split(const string &str, char delim = ' ') {
  stringstream ss(str);
  vector<string> res;
  for (string tmp; getline(ss, tmp, delim);) res.push_back(tmp);
  return res;
}

int main() {
  string line;
  while (cin >> line) {
    auto v = split(line, ',');
    Polygon polygon(4);
    for (int i = 0; i < 4; ++i) polygon[i] = Point(stold(v[2 * i]), stold(v[2 * i + 1]));
    if (area(polygon) < 0) reverse(polygon.begin(), polygon.end());
    auto corners = polygon.getCorners();
    cout << (all_of(corners.begin(), corners.end(), [](array<Point, 3> corner){return ccw(Segment(corner[0], corner[1]), corner[2]) != RIGHT;}) ? "YES" : "NO") << endl;
  }
}

Measured memory_bytes: 3176