// This is free and unencumbered software released into the public domain.

// Anyone is free to copy, modify, publish, use, compile, sell, or
// distribute this software, either in source code form or as a compiled
// binary, for any purpose, commercial or non-commercial, and by any
// means.

// In jurisdictions that recognize copyright laws, the author or authors
// of this software dedicate any and all copyright interest in the
// software to the public domain. We make this dedication for the benefit
// of the public at large and to the detriment of our heirs and
// successors. We intend this dedication to be an overt act of
// relinquishment in perpetuity of all present and future rights to this
// software under copyright law.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
// OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.

// For more information, please refer to <http://unlicense.org>

/****************/
/* template.hpp */
/****************/

#include <algorithm>
#include <cassert>
#include <complex>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <numeric>

using std::abs;
using std::cerr;
using std::cout;
using std::endl;
using std::max;
using std::min;
using std::numeric_limits;
using std::swap;

struct BoolName : std::numpunct<char> {
  std::string t, f;
  BoolName (std::string t, std::string f) : t(t), f(f) {}
  std::string do_truename() const {return t;}
  std::string do_falsename() const {return f;}
};

void set_bool_name(std::string t, std::string f) {
  cout.imbue(std::locale(cout.getloc(), new BoolName(t, f)));
}

struct Initializer {
  Initializer() {
    cout << std::fixed << std::setprecision(15) << std::boolalpha;
    set_bool_name("Yes", "No");
  }
} initializer;

struct Input {
  bool eof;

  Input() : eof(false) {}

  operator char() {
    char v;
    this->eof = (std::scanf("%c", &v) != 1);
    return v;
  }

  operator int() {
    int v;
    this->eof = (std::scanf("%d", &v) != 1);
    return v;
  }

  operator long() {
    long v;
    this->eof = (std::scanf("%ld", &v) != 1);
    return v;
  }

  operator long long() {
    long long v;
    this->eof = (std::scanf("%lld", &v) != 1);
    return v;
  }

  operator double() {
    double v;
    this->eof = (std::scanf("%lf", &v) != 1);
    return v;
  }

  operator long double() {
    long double v;
    this->eof = (std::scanf("%Lf", &v) != 1);
    return v;
  }

  void ignore() const {
    getchar();
  }
} in;

template<typename T> bool chmin(T& a, T b) {return a > b ? a = b, true : false;}

template<typename T> bool chmax(T& a, T b) {return a < b ? a = b, true : false;}

template<typename T, typename S> std::function<S(T)> cast() {
  return [](const T& t) { return static_cast<S>(t); };
}

/******************/
/* arithmetic.hpp */
/******************/

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

  T operator++() {
    return static_cast<T&>(*this) += 1;
  }
};

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 Addition<T>, public Subtraction<T>, public Multiplication<T> {};

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

/*****************/
/* container.hpp */
/*****************/

#include <vector>

template<typename T> class Container : public T {
private:
  using S = typename T::value_type;

public:
  Container() : T() {}

  Container(int n) : T(n) {}

  Container(int n, S s) : T(n, s) {}

  template<typename Itr> Container(Itr first, Itr last) : T(first, last) {}

  Container(const std::initializer_list<S>& v) : T(v) {}

  Container(int n, Input& in) {
    std::vector<S> v(n);
    for (auto& i : v) {
      i = in;
    }
    *this = Container<T>(v.begin(), v.end());
  }

  bool in(const S& a) const {
    return find(this->begin(), this->end(), a) != this->end();
  }
};

/***************/
/* ordered.hpp */
/***************/

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));
  }
};

/**************/
/* vector.hpp */
/**************/

template<typename T> class Vector : public Container<std::vector<T>>, public Arithmetic<Vector<T>>, public Modulus<Vector<T>>, public Ordered<Vector<T>> {
public:
  Vector() = default;

  Vector(const Vector<T>& v) = default;

  Vector(int n) : Container<std::vector<T>>(n) {}

  Vector(int n, T t) : Container<std::vector<T>>(n, t) {}

  template<typename Itr> Vector(Itr first, Itr last) : Container<std::vector<T>>(first, last) {}

  Vector(const std::initializer_list<T>& v) : Container<std::vector<T>>(v) {}

  Vector(int n, Input& in) : Container<std::vector<T>>(n, in) {}

  Vector operator+=(const Vector& v) {
    for (unsigned i = 0; i < this->size(); ++i) (*this)[i] += v[i];
    return *this;
  }

  Vector operator+=(const T& v) {
    for (auto& i : *this) {
      i += v;
    }
    return *this;
  }

  Vector operator-=(const Vector& v) {
    for (unsigned i = 0; i < this->size(); ++i) (*this)[i] -= v[i];
    return *this;
  }

  Vector operator*=(const Vector& v) {
    for (unsigned i = 0; i < this->size(); ++i) (*this)[i] *= v[i];
    return *this;
  }

  Vector operator/=(const Vector& v) {
    for (unsigned i = 0; i < this->size(); ++i) (*this)[i] /= v[i];
    return *this;
  }

  Vector operator%=(const Vector& v) {
    for (unsigned i = 0; i < this->size(); ++i) (*this)[i] %= v[i];
    return *this;
  }

  bool operator<(const Vector& v) const {
    if (this->size() != v.size()) return this->size() < v.size();
    for (unsigned i = 0; i < this->size(); ++i) {
      if ((*this)[i] != v[i]) {
        return (*this)[i] < v[i];
      }
    }
    return false;
  }

  T inner_product(const Vector<T>& v) const {
    return std::inner_product(this->begin(), this->end(), v.begin(), T(0));
  }

  void output(char sep = '\n', char end = '\n') const {
    if (!this->empty()) {
      cout << (*this)[0];
    }
    for (unsigned i = 1; i < this->size(); ++i) {
      cout << sep << (*this)[i];
    }
    cout << end;
  }

  Vector<T> partial_sort(int k, bool reverse = false) {
    if (!reverse) {
      std::partial_sort(this->begin(), this->begin() + k, this->end());
    } else {
      std::partial_sort(this->begin(), this->begin() + k, this->end(), std::greater<T>());
    }
    return *this;
  }

  Vector<T> sort() {
    std::sort(this->begin(), this->end());
    return *this;
  }

  Vector<T> rsort() {
    std::sort(this->rbegin(), this->rend());
    return *this;
  }

  Vector<T> subvector(int a) const {
    return Vector<T>(this->begin(), this->begin() + a);
  }

  Vector<T> subvector(int a, int b) const {
    return Vector<T>(this->begin() + a, this->begin() + b);
  }

  template<typename Function> auto transform(Function func) const -> Vector<decltype(func(T()))> {
    Vector<decltype(func(T()))> res;
    std::transform(this->begin(), this->end(), std::back_inserter(res), func);
    return res;
  }

  Vector<T> partial_sum() const {
    Vector<T> res;
    std::partial_sum(this->begin(), this->end(), std::back_inserter(res));
    return res;
  }

  Vector<T> reverse() {
    std::reverse(this->begin(), this->end());
    return *this;
  }

  template<typename Function> bool all_of(Function func) {
    return std::all_of(this->begin(), this->end(), func);
  }

  Vector<T> adjacent_difference() const {
    Vector<T> res;
    std::adjacent_difference(this->begin(), this->end(), std::back_inserter(res));
    return res;
  }

  T max() const {
    return *max_element(this->begin(), this->end());
  }

  T min() const {
    return *min_element(this->begin(), this->end());
  }

  int argmax() const {
    return max_element(this->begin(), this->end()) - this->begin();
  }

  int argmin() const {
    return min_element(this->begin(), this->end()) - this->begin();
  }
};

template<typename T> Vector<T> iota(int n) {
  Vector<T> v(n);
  std::iota(v.begin(), v.end(), T(0));
  return v;
}

/*********************/
/* bit_operation.hpp */
/*********************/

template<typename T> int least_bit(T n) {
  static_assert(sizeof(T) == 4 || sizeof(T) == 8, "unsupported size");
  if (sizeof(T) == 4) return __builtin_ffs(n) - 1;
  if (sizeof(T) == 8) return __builtin_ffsll(n) - 1;
}

// n must be greater than 0.
template<typename T> int least_bit_fast(T n) {
  static_assert(sizeof(T) == 4 || sizeof(T) == 8, "unsupported size");
  if (sizeof(T) == 4) return __builtin_ctz(n);
  if (sizeof(T) == 8) return __builtin_ctzll(n);
}

template<typename T> int most_bit(T n) {
  static_assert(sizeof(T) == 4 || sizeof(T) == 8, "unsupported size");
  if (sizeof(T) == 4) return n ? 31 - __builtin_clz(n) : -1;
  if (sizeof(T) == 8) return n ? 63 - __builtin_clzll(n) : -1;
}

template<typename T> int count_bit(T n) {
  static_assert(sizeof(T) == 4 || sizeof(T) == 8, "unsupported size");
  if (sizeof(T) == 4) return __builtin_popcount(n);
  if (sizeof(T) == 8) return __builtin_popcountll(n);
}

/******************/
/* math/basic.hpp */
/******************/

template<typename T = double> constexpr T pi() {return acos(T(-1));}

template<typename T> T gcd(T t) {return abs(t);}

template<typename T, typename... S> T gcd(T a, S... s) {
  a = abs(a);
  auto b = gcd(s...);
  if (a == 0 || b == 0) return max(a, b);
  int fa = least_bit_fast(a);
  int fb = least_bit_fast(b);
  a >>= fa;
  b >>= fb;
  while (a != b) {
    auto& c = a > b ? a : b;
    c = abs(a - b);
    c >>= least_bit_fast(c);
  }
  return a << min(fa, fb);
}

template<typename T> T gcd(const Vector<T>& v) {
  T g = abs(v[0]);
  for (int i = 1; i < int(v.size()); ++i) g = gcd(g, v[i]);
  return g;
}

template<typename T> T lcm(T t) {return abs(t);}

template<typename T, typename... S> T lcm(T t, S... s) {
  T l = lcm(s...);
  return abs(t) / gcd(t, l) * l;
}

template<typename T> T lcm(const Vector<T>& v) {
  T l = abs(v[0]);
  for (int i = 1; i < int(v.size()); ++i) l = lcm(l, v[i]);
  return l;
}

template<typename T> T floor(T a, T b) {
  auto d = div(a, b);
  return d.quot - (d.rem && (a < 0) != (b < 0) ? 1 : 0);
}

template<typename T> T ceil(T a, T b) {
  auto d = div(a, b);
  return d.quot + (d.rem && (a > 0) == (b > 0) ? 1 : 0);
}

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

template<typename T> T mod(T a, T b) {
  T c = a % b;
  return c < 0 ? c + abs(b) : c;
}

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

template<typename T> Vector<T> factorial_vector(int n) {
  Vector<T> v(n + 1, 1);
  for (int i = 1; i <= n; ++i) v[i] = v[i - 1] * i;
  return v;
}

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

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

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

template<typename T> bool isSquare(T n) {return square(T(sqrt(n))) == n;}

template<typename T> T clamp(T v, T l, T u) {return v < l ? l : v > u ? u : v;}

/*********************/
/* geometry/real.hpp */
/*********************/

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

public:
  static long double EPS;

  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& 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);}

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

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

long double Real::EPS = 1e-10;

std::ostream& operator<<(std::ostream& os, const Real& a) {
  os << static_cast<long double>(a);
  return os;
}

/**********************/
/* geometry/point.hpp */
/**********************/

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(Input& in) : x(in), y(in) {}

  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);
  }
};

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

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

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

/*********************/
/* geometry/line.hpp */
/*********************/

class Line {
public:
  Point a, b;

  Line() {}

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

  Line(Input& in) : a(in), b(in) {}

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

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

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

/************************/
/* geometry/segment.hpp */
/************************/

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

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

  Segment(Input& in) : Line(in) {}

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

  Real area() const {
    return (this->a.x * this->b.y - this->a.y * this->b.x) / 2;
  }
};

/********************/
/* geometry/ccw.hpp */
/********************/

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;
}

/************************/
/* geometry/polygon.hpp */
/************************/

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

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

  Polygon(int n, Input& in) : Vector<Point>(n, in) {}

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

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

/**************/
/* string.hpp */
/**************/

#include <string>

class String : public std::string {
public:
  String() : std::string() {}

  String(int n) : std::string(std::to_string(n)) {}

  String(const char *s) : std::string(s) {}

  String(const std::string& s) : std::string(s) {}

  String(Input& in) {
    std::cin >> *this;
    in.eof = std::cin.eof();
  }

  static String getline() {
    String v;
    std::getline(std::cin, v);
    in.eof = std::cin.eof();
    return v;
  }

  String reverse() {
    std::reverse(this->begin(), this->end());
    return *this;
  }

  Vector<String> split(char delim = ' ') const {
    std::stringstream ss(*this);
    Vector<String> res;
    for (std::string tmp; std::getline(ss, tmp, delim);) {
      if (tmp != "") res.emplace_back(tmp);
    }
    return res;
  }

  String toupper() const {
    auto s = *this;
    for (auto &c : s) {
      c = std::toupper(c);
    }
    return s;
  }

  template<typename Function> String transform(Function func) const {
    String res;
    std::transform(this->begin(), this->end(), std::back_inserter(res), func);
    return res;
  }

  bool has(const String& s) const {
    return this->find(s) != std::string::npos;
  }

  operator int() const {return std::stoi(*this);}

  operator long double() const {return std::stold(*this);}
};

/************/
/* main.cpp */
/************/

int main() {
  set_bool_name("YES", "NO");
  for (String line; line = in, !in.eof;) {
    auto v = line.split(',').transform(cast<String, long double>());
    Polygon polygon(4);
    for (int i = 0; i < 4; ++i) {
      polygon[i] = Point(v[2 * i], v[2 * i + 1]);
    }
    if (polygon.area() < 0) {
      polygon.reverse();
    }
    auto is_convex = [](Vector<Point> &corner) {
      return ccw(Segment(corner[0], corner[1]), corner[2]) != RIGHT;
    };
    cout << polygon.getCorners().all_of(is_convex) << endl;
  }
}




Measured memory_bytes: 3192