Subtraction of numbers using functions

#include <iostream>
using namespace std;

int subtraction (int a, int b)
{
  int r;
  r=a-b;
  return r;
}

int main ()
{
  int x=5, y=3, z;
  z = subtraction (7,2);
  cout << "The first result is " << z <<endl;
  cout << "The second result is " << subtraction 

(7,2) <<endl;
  cout << "The third result is " << subtraction 

(x,y) <<endl;
  z= 4 + subtraction (x,y);
  cout << "The fourth result is " << z <<endl;
  return 0;
}