#include <sys/msg.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <math.h>

int main(int argc, char *argv[]) {
    char *eptr;
    int count = strtol(argv[1], &eptr, 10);
    int sem = semget(IPC_PRIVATE, count, IPC_CREAT | 0666);
    setbuf(stdin, 0);
    struct sembuf up = {0, 1, 0};
    semop(sem, &up, 1);

    for (int i = 0; i < count; i++) {
        if (!fork()) {
            struct sembuf down = {i, -1, 0};
            while(semop(sem, &down, 1) != -1) {
                int num;
                if (scanf("%d", &num) > 0) {
                    printf("%d %d\n", i, num);
                    fflush(stdout);
                    up.sem_num = abs(num) % count;
                    semop(sem, &up, 1);
                } else {
                    semctl(sem, 0, IPC_RMID, 0);
                    exit(0);
                }
            }
        }
    }
    semop(sem, &up, 1);
    while(wait(NULL) != -1);
    return 0;
}