Decrypt an tex file encrypted with rand()

Question I'm trying to solve

The approach I want to take is to bruteforce all possible keys (seeds) until I find the right one. I know the first characters in the tex file so these are what I'm testing against. When I find the right sequence, I would stop the program and output the key.

/* The ISO/IEC 9899:1990 edition of the C standard */

#include <stdio.h>
#include <time.h>
#include <iostream>

//#define RAND_MAX 32767
static unsigned long int next = 1;
int rand(void) // RAND_MAX assumed to be 32767
{
    next = next * 1103515245 + 12345;
    return (unsigned int)(next/65536) % 32768;
}
void srand(unsigned int seed)
{
    next = seed;
}

using namespace std;

//Return a byte at a time of the rand() keystream
 char randchar() { 
  static int key;
  static int i = 0;

  i = i % 4;
  if (i == 0) key = rand();
  return ((char *)(&key))[i++];
}

int main(int argc, const char* argv[]) {


  for (unsigned int i = time(NULL); i >= 0; i--) //Try all possible return values of time(NULL) since today
  {

      srand(i); 

      cout << "Trying with time(NULL) = " << i << endl;

      FILE *input, *output;
      input = fopen("Homework1b-Windows.tex.enc", "r");
      output = fopen("Homework1b.tex", "w");

      int c,rc, test;
      int pos;
      pos = 0;
      bool pos0, pos1, pos2, pos3, pos4, pos5;
      pos0 = pos1 = pos2 = pos3 = pos4 = pos5 = false;
      char temp1, temp2;

      while ((c = fgetc(input)) != EOF) {
        rc=randchar();
        fputc(c^rc,output);

        test = c^rc;

        temp1 = (char)test;


        temp2 = '\\';

        if ((pos == 0) && (temp1 == temp2))
        {
                 pos0 = true;
        } 

        temp2 = 'd';

        if ((pos == 1) && (temp1 == temp2))
        {
                 pos1 = true;
        }

        /*

        temp2 = 'o';

        if ((pos == 2) && (temp1 == temp2))
        {
                 pos2 = true;
        }

        temp2 = 'c';

        if ((pos == 3) && (temp1 == temp2))
        {
                 pos3 = true;
        }

        */

        temp2 = 'u';

        if ((pos == 4) && (temp1 == temp2))
        {
                 pos4 = true;
        }

        temp2 = 'm';
        if ((pos == 5) && (temp1 == temp2))
        {
                 pos5 = true;
        }

        pos++;

      }
      fclose(input);
      fclose(output);

      if (pos0 && pos1 && pos4 && pos5)
      {
         cout << endl << "Cracked. The seed is time(NULL) = " << i << endl;
         break;
      }
  }

  system("pause");


}

I know that the decrypted tex file starts with "\document".

The problem I'm facing is that the code never terminates. It never finds the right key (seed).

Any help?

Thank you.