Uva 10168 - Summation of Four Primes

 /*
Verdict :: Accepted

*/
/// Header file begin
#include <iostream>
#include <cstdio>
#include <cstring>
#include <map>
#include <string>
#include <vector>
#include <cmath>
#include <cctype>
#include <sstream>
#include <set>
#include <list>
#include <stack>
#include<utility>
#include <queue>
#include <algorithm>
/// End
//..........
/// Macro
#define sf scanf
#define pf printf
#define sfint(a,b) scanf("%d %d",&a,&b)
#define sfl(a,b) scanf("%ld %ld",&a,&b)
#define sfll(a,b) scanf("%lld %lld",&a,&b)
#define sfd(a,b) scanf("%lf %lf",&a,&b)
#define sff(a,b) scanf("%f %f",&a,&b)
#define lp1(i,n) for(i=0;i<n;i++)
#define lp2(i,n) for(i=1;i<=n;i++)
#define mem(c,v) memset(c,v,sizeof(c))
#define cp(a) cout<<" "<<a<<" "<<endl
#define nl puts("")
#define sq(x) ((x)*(x))
#define all(x) x.begin(),x.end()
#define sz size()
#define gc getchar()
#define pb push_back
/// End.........

/// Size
#define mx7 20000100
#define mx6 1500000
#define mx5 100005
#define mx4 1000100
#define inf 1<<30                                           //infinity value
#define eps 1e-9
#define mx 10000000
#define mod 1000000007
#define pi acos(-1.0)

/// Macros for Graph

#define white 0
#define gray 1
#define black -1
#define nil -2

using namespace std;
//..................................................................................................................
typedef long long LL;
typedef long L;
typedef unsigned long long ull;
typedef unsigned long ul;
typedef unsigned int ui;
typedef pair<int, int> pii;

template<class T> T gcd(T a, T b ) {return b<=0?a:gcd(b,a%b);}
template<class T> T large(T a, T b ) {return a>b?a:b;}
template<class T> T small(T a, T b ) {return a<b?a:b;}
template<class T> T diffrnce(T a, T b) {return a-b<0?b-a:a-b;}

int prime[(mx>>6)+1],prm[(mx>>1)+1],plen=0;

#define setbit(n) (prime[n>>6]|=(1<<((n>>1)&31)))
#define checkbit(n) (prime[n>>6]&(1<<((n>>1)&31)))

void seieve(int n)
{
    int i,j,x=(int)sqrt(double(n));

    for(i=3;i<=x;i+=2)
    {
        if(!checkbit(i))
        {
            for(j=i*i;j<=n;j+=i+i)
            {
                setbit(j);
            }
        }
    }

    prm[plen++]=2;

    for(i=3;i<=n;i+=2)
    {
        if(!checkbit(i))
        {
            prm[plen++]=i;
        }
    }

    //lp1(i,plen)cp(prm[i]);
}

bool isPrime(int n)
{
    if(n==2) return true;
    else if(!(n&1) or n<2) return false;
    else
    {
        return !checkbit(n);
    }
    return true;
}

vector<int>v;

int vlen;

void chk(int n)
{
    bool f=false;

    for(int i=0;i<plen;i++)
    {
        if((n>>1) >= prm[i])
        {
            int b=n-prm[i];

            if(isPrime(b))
            {
                if(b+prm[i] == n)
                {
                    //pf("%d %d ",prm[i],b);
                    v.push_back(prm[i]);
                    v.push_back(b);
                    //v[vlen++]=prm[i];
                    //v[vlen++]=b;
                    f=true;
                    break;
                }
            }
        }
    }
}

int main()
{
    seieve(mx);
    int n;
    while(~sf("%d",&n))
    {
        if(n<=7)
        {
            pf("Impossible.\n");
            continue;
        }

        if(!(n&1)) // subtract 4 if n is an even
        {
            int b = n-4;

            chk(b);
            chk(4);
        }

        else
        {
            int b=n-5; // subtract 5 if n is an odd
            chk(b);
            chk(5);
        }

        vlen=v.size();

        int s=0,sp=vlen;

        sort(all(v));

        for(int i=0;i<vlen;i++)
        {
            pf("%d",v[i]);
            s+=v[i];
            if(sp>1)
            {
                pf(" ");
                sp--;
            }
        }

        //cout << " sum = " << s;
        //vlen=0;
        v.clear();
        nl;
    }

    return 0;
}