#include <stdio.h>

main(argc, argv)
int argc;
char **argv;
{
  FILE *inf,*opf;
  int i,j;
  int ival[4];

  if (argc > 1)  
    inf=fopen(argv[1],"r");
  else
    inf=stdin;
  if (argc > 2)
    opf=fopen(argv[2],"w");
  else
    opf=stdout;

  i=0;
  while ((ival[i++]=fgetc(inf)) != EOF) {
    if (i%4 == 0) {
      for (j=0; j<4; j++) fputc(ival[3-j],opf);
      i=0;
    }
  }
}