#include<iostream> 
using namespace std; 
class InvalidInputException : public exception {
  public:
    const char* what() const throw() {
      return "Invalid input. Please enter a valid number and a non-negative integer.";
    }
};
double Power(double n,int p=2) 
{ 
  double ans=1; 
  if(p==0) 
    return ans; 
  else 
  {   
    for(int i=1;i<=p;i++) 
    { 
      ans=ans*n; 
    } 
    return ans; 
  } 
} 
double Recurse(double n,int p=2) 
{ 
  if(p==0) 
  { 
    return 1; 
  } 
  if(p==1) 
  { 
    return n; 
  } 
  else 
  { 
    return (n*Recurse(n,p-1)); 
  } 
} 

int main() 
{ 
  double n; 
  int p; 
  cout<<"Enter the base value (power is default set to 2) :"; 
  try {
    cin>>n; 
    // Check if the input is valid
    if(cin.fail()) {
      cin.clear();
      cin.ignore(1000, '\n');
      throw InvalidInputException();
    }
    cout<<"Power of number is : "<<Power(n)<<endl; 
  }
  catch(InvalidInputException& e) {
    // Print the error message
    cout<<e.what()<<endl;
  }
  
  cout<<"\nEnter the base value and power :"; 
  try {
    cin>>n>>p; 
    // Check if the input is valid
    if(cin.fail() || p < 0) {
      // Clear the input stream and throw an exception
      cin.clear();
      cin.ignore(1000, '\n');
      throw InvalidInputException();
    }
    cout<<"Power of number is : "<<Power(n,p)<<endl; 
  }
  catch(InvalidInputException& e) {
    // Print the error message
    cout<<e.what()<<endl;
  }
  
  cout<<"\nEnter the base value and power :"; 

  try {
    cin>>n>>p; 
    // Check if the input is valid
    if(cin.fail() || p < 0) {
      
      cin.clear();
      cin.ignore(1000, '\n');
      throw InvalidInputException();
    }
    cout<<"Using Recursion, Power of number is : "<<Recurse(n,p)<<endl; 
  }
  catch(InvalidInputException& e) {
    // Print the error message
    cout<<e.what()<<endl;
  }
  return 0; 
}