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

enum { BASE = 10, INIT = 123456 };
int main(int argc, char *argv[]) {
    setbuf(stdin, NULL);
    int nproc = strtol(argv[2], NULL, BASE);
    key_t key = INIT;
    int semid = semget(key, nproc, 0666 | IPC_CREAT);
    if (semid < 0) {
        exit(errno);
    }
    pid_t p;
    u_int32_t x;
    int fd = open(argv[1], O_RDONLY);
    for (int i = 0; i < nproc; ++i) {
        if ((p = fork()) == -1) {
            exit(errno);
        }
        if (!p) {
            u_int32_t sum = 0;
            off_t offset = lseek(fd, 0, SEEK_END);
            off_t cur = i * sizeof(x);
            while (cur < offset) {
                lseek(fd, cur, SEEK_SET);
                cur += nproc * sizeof(x);
                read(fd, &x, sizeof(x));
                sum += x;
            }
            semop(semid, (struct sembuf[]){{i, -1, 0}}, 1);
            printf("%u\n", sum);
            fflush(stdout);
            if (i < nproc - 1) {
                semop(semid, (struct sembuf[]){{i + 1, 1, 0}}, 1);
            }
            _exit(0);
        }
    }
    semop(semid, (struct sembuf[]) {{0, 1, 0}}, 1);
    while(wait(NULL) > 0) {
    }
    semctl(semid, 0, IPC_RMID);
}