C++ Round Half Down

Simple C++ program to round given number half down.

#include <iostream>
#include <cmath>

using namespace std;

// 2018 TheFlyingKeyboard and released under MIT License
// theflyingkeyboard.net
double roundHalfDown(double x, int n);

int main() {
  double x = 0;
  int n = 0;

  cout << "Enter x: ";
  cin >> x;


  cout << "Enter n: ";
  cin >> n;

  cout << "roundHalfDown(" << x << ", " << n << ") is equal to " << roundHalfDown(x, n);

  int a;
  cin >> a;

  return 0;
}

double roundHalfDown(double x, int n) {
  return ceil(pow(10, n) * x - 0.5f) / pow(10, n);
}

IN
20.5 0
-20.5 0
OUT
20
-21