C++: Creating Custom Exceptions

 #include <cmath>  
 #include <iostream>  
 #include <exception>  
 #include <stdexcept>  
 using namespace std;  

 struct MyException : public exception  
 {  
  const char * what () const throw ()  
  {  
   return "n and p should be non-negative";  
  }  
 };  

 class Calculator{  
   public:  
   int power(int n, int p){  
    if(n>=0 && p>=0){  
      return pow(n,p);  
    }else{  
      throw MyException();  
    }  
   }  
 };  

 int main()  
 {  
   Calculator myCalculator=Calculator();  
   int T,n,p;  
   cin>>T;  
   while(T-->0){  
    if(scanf("%d %d",&n,&p)==2){  
      try{  
         int ans=myCalculator.power(n,p);  
         cout<<ans<<endl;   
      }  
      catch(exception& e){  
        cout<<e.what()<<endl;  
      }  
    }  
   }  
 }