main(){
   char a[25],ch,temp;
   int i;
   clrscr();
   printf ("\nEnter the string:-> ");
   gets(a);
   for (i=0;a[i]!='\0';i++){
      if (a[i+1]=='\0')break;
      temp=a[i];
      a[i]=a[i+1];
      a[i+1]=temp;
      i++;
   }
   puts(a);
   getch();
}