#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

#define CHLDMAX 4


int
main(int argc, char *argv[])
{
	char c, buf[2];
	int status, nchlds=0;
	pid_t pid;

	if (argc != 2) {
		fprintf(stderr, "usage: %s DIFFICULTY\n", *argv);
		exit(1);
	}

	for (c='a'; ; c++) {
		if (c > 'z') {
			c = 'a';
		}
		if (nchlds == CHLDMAX) {
			wait(&status);
			nchlds--;
			if (WIFEXITED(status) && WEXITSTATUS(status)==0) {
				/* our work is done */
				break;
			}
		}
		fflush(stdout);
		pid = fork();
		nchlds++;
		if (pid == -1) {
			perror("fork");
			exit(1);
		}
		if (pid == 0) {  /* child */
			srand(getpid());
			buf[0] = c;
			buf[1] = '\0';
			execl("miner", "miner", argv[1], buf, (char *)NULL);
			perror("exec");
			exit(1);
		}
	
	}
	while (wait(&status) != -1) {
		continue;
	}
	return 0;
}