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

sig_atomic_t value = 0;
sig_atomic_t flag = 0;

void sigterm_handler(int sig)
{
    flag = 1;
}

void sigusr1_handler(int sig)
{
    value++;
}

void sigusr2_handler(int sig)
{
    value *= -1;
}

int main()
{
    struct sigaction sigusr1_act = {
        .sa_handler = sigusr1_handler,
        .sa_flags = SA_RESTART,
        .sa_mask = 0,
    };
    struct sigaction sigusr2_act = {
        .sa_handler = sigusr2_handler,
        .sa_flags = SA_RESTART,
        .sa_mask = 0,
    };
    struct sigaction sigterm_act = {
        .sa_handler = sigterm_handler,
        .sa_flags = SA_RESTART,
    };
    sigaction(SIGUSR1, &sigusr1_act, NULL);
    sigaction(SIGUSR2, &sigusr2_act, NULL);
    sigaction(SIGTERM, &sigterm_act, NULL);
    printf("%d\n", getpid());
    fflush(stdout);
    scanf("%d", &value);
    for (;;) {
        pause();
        if (flag == 1) {
            break;
        }
        printf("%d\n", value);
        fflush(stdout);
    }
    return 0;
}