#include <stdio.h>
#include <stdlib.h>

FILE *r = NULL, *g = NULL, *b = NULL;

void ciao(int v)
{
  if (r!=NULL) fclose(r);
  if (g!=NULL) fclose(g);
  if (b!=NULL) fclose(b);
  exit(v);
}

help()
{
  fprintf(stderr,"interp R G B\n");
  exit(1);
}

int main(int argc, char **argv)
{
  int go=1, cr, cg, cb;

  if ( argc < 4 ) help();

  r = fopen(argv[1], "rb");
  g = fopen(argv[2], "rb");
  b = fopen(argv[3], "rb");

  if ( (r==NULL) || (g==NULL) || (b==NULL) ) ciao(1);

  while(1)
  {
    cr = fgetc(r);
    cg = fgetc(g);
    cb = fgetc(b);
    if ( (cr==EOF) && (cg==EOF) && (cb==EOF) ) break;
    cr = (cr==EOF)? 0 : cr;
    cg = (cg==EOF)? 0 : cg;
    cb = (cb==EOF)? 0 : cb;
    putchar(cr); putchar(cg); putchar(cb);
  }
  ciao(0);
}