#include <iostream>
#include <cassert>
using namespace std;

void swap(int& a, int& b)
{ int temp = a; a = b; b = temp; }

int gcd(int a, int b){
   assert (a || b);
   if ( a < 0 ) a = -a;
   if ( b < 0 ) b = -b;
   if ( a < b ) swap(a,b);
   if ( b == 0 ) return a;

   int r = a%b;
   if (r == 0) return b;
   else return gcd(b, r);  // Check it.
}

class Fraction{ 
   public:
      Fraction(int, int);            // Constructor. 
      Fraction():n(0),d(1){}         // Default Constructor. 
      int top() const { return n; }  // Accessor.
      int bot() const { return d; }  // Accessor.

      // const Fraction& operator=( const Fraction& ); 
      // Automatically generated --- no need to implement here. 

      const Fraction& operator+=( const Fraction& );  // Mutator.
      istream& get(istream&);         // Input.
      ostream& put(ostream&) const;   // Output.

   private:                           // Clients cannot touch these.
      int n, d;
};

istream& operator>>( istream& is, Fraction& f){
   f.get(is);  return is;
}

ostream& operator<<( ostream& os, const Fraction& f){
   f.put(os);  return os;
}

Fraction::Fraction(int n0, int d0){
   assert (d0);
   if (d0 < 0) {   // For definiteness, always store 
      d0 = -d0;    //  the denominator as positive.
      n0 = -n0;
   }
   int g = gcd(n0,d0);
   n = n0/g;
   d = d0/g;
}

istream& Fraction::get(istream& is){   // Input.
  int n0,d0; // temporaries.
  is >> n0; 
  char ch;
  if (is){ is >> ch; assert(ch == '/');  }
  if (is) is >> d0;   // Enforce format.
  if (is) { 
     int g = gcd(n0,d0);
     n = n0/g;  d = d0/g;
  }
  return is;
}

ostream& Fraction::put(ostream& os) const {   // Output.
   os << n << '/' << d;
   return os;
}

Fraction operator+(const Fraction& f, const Fraction& g ){
    if ( f.top() == 0 ) return g;
    else if ( g.top() == 0 ) return f;
    else
       return Fraction( f.top()*g.bot() + f.bot()*g.top(), f.bot()*g.bot() );
}

const Fraction& Fraction::operator+=(const Fraction& g ){
    int n0 = n*g.d + d*g.n;
    int d0 =  d*g.d ;
    int fac = gcd(n0,d0);
    n = n0/fac;  d = d0/fac;
    return *this;
}

Fraction operator-(const Fraction& f){
   return Fraction(-f.top(), f.bot());
}

Fraction operator-(const Fraction& f, const Fraction& g ){
    if ( f.top() == 0 ) return -g;
    else if ( g.top() == 0 ) return f;
    else
       return Fraction( f.top()*g.bot() - f.bot()*g.top(), f.bot()*g.bot() );
}

Fraction operator*(const Fraction& f, const Fraction& g ){
   return Fraction( f.top()*g.top(),  f.bot()*g.bot() );
}

Fraction operator/(const Fraction& f, const Fraction& g ){
   return Fraction( f.top()*g.bot(),  f.bot()*g.top() );
}

bool operator==( const Fraction& f, const Fraction& g ){
    return (f.top()==g.top()) && (f.bot()==g.bot());
}

bool operator!=( const Fraction& f, const Fraction& g ){
    return !(f==g);
}

bool operator<=( const Fraction& f, const Fraction& g ){
    return (f.top()*g.bot() <= f.bot()*g.top());
}

bool operator>=( const Fraction& f, const Fraction& g ){
    return (f.top()*g.bot() >= f.bot()*g.top());
}

bool operator>( const Fraction& f, const Fraction& g ){
    return (f.top()*g.bot() > f.bot()*g.top());
}

bool operator<( const Fraction& f, const Fraction& g ){
    return (f.top()*g.bot() < f.bot()*g.top());
}

int main(){   // Test driver.
   Fraction f, g, h;
   cout << "Enter two fractions, separated by spaces only: ";
   f.get(cin);
   g.get(cin);
   cout << "f = "; f.put(cout); 
   cout << "  g = "; g.put(cout); 
   cout << endl;

   cout << "f + g = ";
   h = f+g;  h.put(cout); cout << endl;
   cout << "f - g = ";
   h = f-g;  h.put(cout); cout << endl;
   cout << "f * g = ";
   h = f*g;  h.put(cout); cout << endl;
   cout << "f / g = ";
   h = f/g;  h.put(cout); cout << endl << endl;

   if ( f == g ) cout << " f == g.\n";
   else if ( f < g ) cout << " f < g.\n";
   else if ( f > g ) cout << " f > g.\n";
   else              
     cout << "Error in comparing f and g.\n";

   f += g;
   cout << "\nAfter f+=g, f = " << f << ".\n"; 
   return 0;
}

/*   Sample I/O.
Enter two fractions, separated by spaces only: 24/56 56/96 
f = 3/7  g = 7/12
f + g = 85/84
f - g = -13/84
f * g = 1/4
f / g = 36/49

 f < g.

After f+=g, f = 85/84.
*/