#include <iostream>
 #include <cmath>
 using namespace std;
 
 double balance; 
 /** 
    Accumulates interest in the global variable balance
    @param p the interest rate in percent
    @param n the number of periods the investment is held
 */
 void future_value(int p, int n)
 {  balance = balance * pow(1 + p / 100, n); 
 }
 
 int main()
 {  balance = 10000;
    future_value(5, 10);
    cout << "After ten years, the balance is "
         << balance << "\n";
    return 0;
 }