Dear experts, I am trying to solve this, put solution comes up as incorrect all the time. Please help here.

#include 

// INSERT YOUR SOLUTION

 } // look-up of the value associated with key V const& operator[]( K const& key ) const { auto it=m_map.upper_bound(key); if(it==m_map.begin()) { return m_valBegin; } else { return (--it)->second; } } }; // Many solutions we receive are incorrect. Consider using a randomized test // to discover the cases that your implementation does not handle correctly. // We recommend to implement a test function that tests the functionality of // the interval_map, for example using a map of int intervals to char.