#include<stdio.h>
#include<string.h>
#define SIZE 1000 

void reverse(char s[]);

int main()
{
  char s[SIZE]="HELLO WORLD!";
  reverse(s);
  printf("%s\n",s);

return 0;
}

void reverse(char s[])
{
 int c, i, j;

  for(i=0,j=strlen(s)-1; i<j; i++,j--)
   {
        c=s[i];  s[i]=s[j];  s[j]=c;
   }
}