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


volatile sig_atomic_t last;

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

void
handler2(int s)
{
    _exit(0);
}

void
handler1(int s)
{
    static volatile sig_atomic_t counter = 0;
    counter++;
    if (counter >= 4) {
        _exit(0);
    }
    printf("%d\n", last);
    fflush(stdout);
}

int
main(int argc, char *argv[])
{
    sigaction(SIGINT, &(struct sigaction) { .sa_handler = handler1, .sa_flags = SA_RESTART }, NULL);
    sigaction(SIGINT, &(struct sigaction) { .sa_handler = handler2, .sa_flags = SA_RESTART }, NULL);
    int low, high;
    last = 0;
    scanf("%d", &low);
    scanf("%d", &high);
    printf("%d\n", getpid());
    fflush(stdout);
    for (int i = low; i < high; ++i) {
        if (is_prime(i)) {
            last = i;
        }
    }
    printf("-1\n");
    fflush(stdout);
    return 0;
}