# 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;
      printf("in swap u = %d, v = %d\n",u,v);
      temp = u;
      u = v;
      v = temp;
      printf("in swap u = %d, v = %d\n",u,v);
      return;
    }