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I kept getting an segmentation fault, so I think I need to decrease memory usage but I am unsure of how. I am using the Sieve of Atkins to calculate prime numbers and then testing the primes against 600851475143 (Project Euler). Here is my code so far:

```
#include <iostream>
#include <cmath>
using namespace std;
int main (int argc, char* argv[])
{
//Create the various different variables required
long long limit = 300000000000;
int root = ceil(sqrt(limit));
bool sieve[limit];
int primes[(limit/2)+1];
int insert = 2;
primes[0] = 2;
primes[1] = 3;
for (int z = 0; z < limit; z++) sieve[z] = false;
for (int x = 1; x <= root; x++)
{
for (int y = 1; y <= root; y++)
{
//Main part of Sieve of Atkin
int n = (4*x*x)+(y*y);
if (n <= limit && (n % 12 == 1 || n % 12 == 5)) sieve[n] ^= true;
n = (3*x*x)+(y*y);
if (n <= limit && n % 12 == 7) sieve[n] ^= true;
n = (3*x*x)-(y*y);
if (x > y && n <= limit && n % 12 == 11) sieve[n] ^= true;
}
}
//Mark all multiples of squares as non-prime
for (int r = 5; r <= root; r++) if (sieve[r]) for (int i = r*r; i < limit; i += r*r) sieve[i] = false;
//Add into prime array
for (int a = 5; a < limit; a++)
{
if (sieve[a])
{
primes[insert] = a;
insert++;
}
}
long long number = 600851475143;
long long x;
int y = 0;
int answer[x];
for(x=0;x<300500000000;x++){
if(number % primes[x] == 0){
answer[y] = primes[x];
y++;
}else{
}
}
cout<<answer[y];
}
//Create the various different variables required
long long limit = 300000000000;
int root = ceil(sqrt(limit));
bool sieve[limit];
int primes[(limit/2)+1];
int insert = 2;
primes[0] = 2;
primes[1] = 3;
for (int z = 0; z < limit; z++) sieve[z] = false;
for (int x = 1; x <= root; x++)
{
for (int y = 1; y <= root; y++)
{
//Main part of Sieve of Atkin
int n = (4*x*x)+(y*y);
if (n <= limit && (n % 12 == 1 || n % 12 == 5)) sieve[n] ^= true;
n = (3*x*x)+(y*y);
if (n <= limit && n % 12 == 7) sieve[n] ^= true;
n = (3*x*x)-(y*y);
if (x > y && n <= limit && n % 12 == 11) sieve[n] ^= true;
}
}
//Mark all multiples of squares as non-prime
for (int r = 5; r <= root; r++) if (sieve[r]) for (int i = r*r; i < limit; i += r*r) sieve[i] = false;
//Add into prime array
for (int a = 5; a < limit; a++)
{
if (sieve[a])
{
primes[insert] = a;
insert++;
}
}
long long number = 600851475143;
long long x;
int y = 0;
int answer[x];
for(x=0;x<300500000000;x++){
if(number % primes[x] == 0){
answer[y] = primes[x];
y++;
}else{
}
}
cout<<answer[y];
}
```