#include <unistd.h>
#include <stdio.h>
#include <stdint.h>
#include <signal.h>

uint32_t one = 1;
volatile int flag1 = 0;
volatile int flag2 = 0;
volatile int counter = 0;
uint32_t mask_host = ((uint32_t) 1 << 16) - 1;
uint32_t mask_net = ((uint32_t) 1 << 30) - ((uint32_t) 1 << 16);

int is_ipv4B(uint32_t addr) {
    if ((addr & (one << 31)) && !(addr & (one << 30))) {
        return 1;
    }
    return 0;
}

uint32_t get_elem(uint32_t addr) {
    uint32_t res;
    if (flag1) {
        res = addr & mask_host;
    } else {
        res = (addr & mask_net) >> 16;
    }
    return res;
}

void handler(int signo) {
    if (signo == SIGUSR1) {
        flag1 = !flag1;
        ++counter;
        if (counter == 5) {
            _exit(0);
        }
    } else if (signo == SIGUSR2) {
        flag2 = 1;
    }
}


int main() {
    struct sigaction sa = { .sa_handler = handler, .sa_flags = SA_RESTART };
    sigaction(SIGUSR1, &sa, NULL);
    sigaction(SIGUSR2, &sa, NULL);

    sigset_t mask1, mask2;
    sigemptyset(&mask1);
    sigaddset(&mask1, SIGUSR1);
    sigaddset(&mask1, SIGUSR2);
    sigprocmask(SIG_BLOCK, &mask1, &mask2);

    printf("%d\n", getpid());
    fflush(stdout);
    while (1) {
        while (!flag2) {
            sigsuspend(&mask2);
        }
        if (flag2) {
            uint32_t num;
            scanf("%o", &num);
            if (is_ipv4B(num)) {
                printf("%u\n", get_elem(num));
            } else {
                printf("0\n");
            }
            fflush(stdout);
        }
        flag2 = 0;
        break;
    }
}