#include <iostream>
using namespace std;

int sum(int (*)(int), int);
int square(int);
int cube(int);

int main()
{
  cout << sum(square,4) << endl;
  // 1 + 4 + 9 + 16
  cout << sum(cube,4) << endl;
  // 1 + 8 + 27 + 64
}

int sum(int (*pf)(int k), int n)
{ // returns the sum f(0) + f(1) + f(2) + . . . + f(n-1):
  int s = 0;
  for (int i = 1; i <= n; i++)
    s += (*pf)(i);
  return s;
}
int square(int k)
{
  return k*k;
}
int cube(int k)
{
  return k*k*k;
}