#include <iostream>
#include <stdexcept>
#include <cmath>
using namespace std;
 
class FutureValueError : public logic_error {
public:
   FutureValueError(const char reason[]);
};

FutureValueError::FutureValueError(const char reason[])
   : logic_error(reason){}

double future_value(double initial_balance, double p, int n)
{  if (p < 0 || n < 0)
     throw FutureValueError("illegal future_value parameter");
   return initial_balance * pow(1 + p / 100, n);
}

void read(double& init, double& interest, int& years)
{  cout << "Enter initial value, interest and years: ";
   cin >> init >> interest >> years;
   if (years > 100) throw logic_error("too many years!");
   cout << init << " " << interest << " " << years << endl;
}

int main()
{  bool more = true;
   while (more)
    {  double init, interest;
       int years;
       try
       {  read(init, interest, years);
          double fvalue = future_value(init, interest, years); 
          cout << "The future value is " << fvalue << endl;  
       }
       /**/
       catch (FutureValueError& e)
       {  cout << "A FutureValueError has occurred: "
               << e.what() << "\n";
       } 
       /**/      
       catch (logic_error& e)
       {  cout << "A logic error has occurred: "
               << e.what() << "\n";
       }       
       cout << "Retry? (y/n)";
       char input;
       cin >> input;
       if (input == 'n') more = false;
    } 
    return 0;
 }