#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <unistd.h>

typedef struct {
  pthread_mutex_t *lock;
  int n;
  int running;
} Info;

void *waiter(void *arg)
{
  Info *I;
  int status;

  I = (Info *) arg;

  while (1) {
    wait(&status);
    pthread_mutex_lock(I->lock);
    I->running--;
    if (I->running < I->n) {
      if (fork() == 0) { execlp("experiment", "experiment", NULL); exit(1); }
      I->running++;
    }
    pthread_mutex_unlock(I->lock);
  }
}

main()
{
  Info I;
  pthread_t tid;
  int new_n, i;

  I.lock = (pthread_mutex_t *) malloc(sizeof(pthread_mutex_t));
  pthread_mutex_init(I.lock, NULL);
  I.n = 0;
  I.running = 0;

  while (1) {
    if (scanf("%d", &new_n) != 1 || new_n <= 0) exit(0);
    pthread_mutex_lock(I.lock);
    while (I.running < new_n) {
      if (fork() == 0) { execlp("experiment", "experiment", NULL); exit(1); }
      I.running++;
    }
    if (I.n == 0) pthread_create(&tid, NULL, waiter, (void *) &I);
    I.n = new_n;
    pthread_mutex_unlock(I.lock);
  }
}