Decker Mutual-Exclusion

I'm studying the operating system and the program that Decker wrote for his third attempt to Mutual Exclusion I wrote my code in C ++ in Visual Studio, the code is below, but I wonder how these two threads are still in the critical area at the same time? The output of the program is below

#include<iostream>
#include<conio.h>
#include<thread>
using namespace std;

bool flag0 = false;
bool flag1 = false;

void p1()
{
    flag0 = true;
    while (flag1);
    for (int i = 1; i <= 10; i++)
        cout << "p1 : " << i << endl;
    flag0 = false;

}

void p2()
{
    flag1 = true;
    while (flag0);
    for (int i = -1; i >= -10; i--)
        cout << "p2 : " << i << endl;
    flag1 = false;
}

int main()
{

    thread t1(p1);
    thread t2(p2);


    t1.join();
    t2.join();

    _getch();
    return 0;
}

Output:

p1 : p2 : -11

p2 : p1 : 2
p1 : 3
p1 : 4
p1 : 5
p1 : 6
-2
p2 : -3
p2 : -4
p2 : -5
p2 : -6
p2 : -7
p2 : -8
p2 : -9
p2 : p1 : -107
p1 : 8
p1 : 9
p1 : 10