11-5

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

volatile sig_atomic_t sgnt = 0;
volatile sig_atomic_t easy = 0;

void
sig_hndl(int sig)
{

    if (sig == SIGINT) {
        sgnt++;
        if (sgnt >= 4) {
            exit(0);
        } else {
            printf("%d\n", easy);
            fflush(stdout);
        }
    } else if (sig == SIGTERM) {
        exit(0);
    }
}

int
is_easy(int num)
{
    if (num == 1) {
        return 0;
    }
    int i;
    for (i = 2; num % i && i * i < num; i++);
    if (num % i) {
        return 1;
    }
    return 0;
}

int
main(void)
{
    sigaction(SIGINT, &(struct sigaction) { .sa_handler = sig_hndl, .sa_flags = SA_RESTART }, NULL);
    sigaction(SIGTERM, &(struct sigaction) { .sa_handler = sig_hndl, .sa_flags = SA_RESTART }, NULL);
    int low, high;
    scanf("%d%d", &low, &high);
    printf("%d\n", getpid());
    int i;
    for (i = low; i < high; i++) {
        if (is_easy(i)) {
            easy = i;
        }
    }
    printf("-1\n");
    fflush(stdout);
    return 0;
}