reading line in c++

#include <bits/stdc++.h>
typedef long long ll;
# define FAST_CODE ios_base::sync_with_stdio(false); cin.tie(NULL);
# define pb push_back
using namespace std;
const ll n = 10000001;

vector <ll> Prime;

bool is_composite[n];
bool is_prime[n];

void linear_sieve ()
{
	std::fill (is_composite, is_composite + n, false);
	for (ll i = 2; i < n; ++i) 
	{
		if (!is_composite[i]) 
		{
			Prime.push_back (i);
			is_prime[i] = true;
		}
		for (ll j = 0; j < Prime.size () && i * Prime[j] < n; ++j) 
		{
			is_composite[i * Prime[j]] = true;
			if (i % Prime[j] == 0) break;
		}
	}
}

int main() 
{

	FAST_CODE
  
  /*
  you have to read integrs on each line and you have to tell weather they can expressed as a summation of 4 primes
  https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1109
  summation of four primes UVA
  */
	
	linear_sieve();
	
	string s;
	
	while(getline(cin, s))
	{
		stringstream geek(s);
		ll x;
		geek>>x;
		// cout<<x<<endl;
		if(x<8)
		{
			cout<<"Impossible."<<endl;
			continue;
		}
		
		if(x%2==0)
		{
			x-=4;
			cout<<2<<" "<<2<<" ";
		}
		
		else if(x%2!=0)
		{
			x-=5;
			cout<<2<<" "<<3<<" ";
		}
		
		for(ll i=2; i<=x/2; i++)
		{
			if(is_prime[i] && is_prime[x-i])
			{
				cout<<i<<" "<<x-i<<endl;
				break;
			}
		}
	}
	
	return 0;
}