#include <cstdio>
#include <future>
#include <atomic>

volatile char data[64 * 3];
volatile char &a = data[64];
volatile char &b = data[64*2];
std::atomic<int_fast8_t> barrier;

char th1() {
    char vA;

    barrier++;
    while (barrier != 2);

    b = 1;
    vA = a;

    return vA;
}
    
char th2() {
    char vB;

    barrier++;
    while (barrier != 2);

    a = 1;
    vB = b;

    return vB;
}

int main() {
    auto a1 = std::async(th1);
    auto a2 = std::async(th2);

    char vA = a1.get();
    char vB = a2.get();

    printf("%d %d\n", vA, vB);
    return 0;
}