# include <stdio.h>

    void swap(int &, int &); /* declaration */
    int main()
    {
      int x = 15, y = 42;
      printf("x = %d, y = %d\n", x, y);
      swap(x,y);
      printf("x = %d, y = %d\n", x, y);
    }
    
       
    void swap(int &u, int &v)
    {
      int temp;
      temp = u;
      u = v;
      v = temp;
      return;
    }