#include <iostream>
#include <stdio.h>
#include <math.h>
#include <thread>
#include <vector>

using namespace std;

const int N = 999;
const int l_watkow = 4;

unsigned char tab[N][N][3];

int ulam_get_map(int x, int y, int n)
{
    x -= (n-1)/2;
    y -= n/2;

    int mx = abs(x), my = abs(y);
    int l = 2*max(mx, my);
    int d = y >= x ? l*3 + x + y : l - x - y;

    return pow(l-1,2)+d;
}

int isprime(int n)
{
    for (int p = 2; p*p <= n; p++)
        if (n % p == 0) return 0;          
    return n > 2;
}


int main()
{
	auto ulam=[](int x, int y)
	{
    for (int i = x; i < x + 0.5*N; i++)
    	for (int j = y; j < y + 0.5*N; j++)
        	if (isprime(ulam_get_map(i, j, N)))
            	for (int k=0;k<3;k++) tab[i][j][k] = 0;
        	else
            	for (int k=0;k<3;k++) tab[i][j][k] = 255;
	};
   vector<thread> v;
  
   for (int i = 0; i < l_watkow; i++)
   {
   		 int x = 2*N*(i%2)/l_watkow;
         int y = 2*N*int(i/2)/l_watkow;
   		 v.push_back(thread(ulam, x, y));
   }

   for (int i = 0; i < l_watkow; i++) v[i].join();
   
   FILE *fp= fopen("39247_lab4_poprawione.ppm","wb");
   fprintf(fp,"P6\n %s\n %d\n %d\n %d\n","# ",N,N,255);
   for (int i = 0; i < N; i++)
      for (int j = 0; j < N; j++)
         fwrite(tab[i][j],1,3,fp);
   fclose(fp);
   return 0;
}