#ifndef _PAIR_HASH_H_
#define _PAIR_HASH_H_

#include <cstdlib>
#include <functional>
#include <utility>

class A {
   
   
   private:
   
   struct PairHash {
      
      
      public:
      template <typename T, typename U>
      std::size_t operator()(std::pair<T, U> const & x) const {
         
         return std::hash<T>()(x.first) ^ std::hash<U>()(x.second);
      }
   };
};

#endif
