poj 3292 Semi-prime H-numbers

http://poj.org/problem?id=3292

#include<iostream>

#include<cstring>

#include<string>

#include<cstdio>



using namespace std;



const int N=1000001;

int ans[N];

void findans()

{

    memset(ans,0,sizeof(ans));

    for(int i=5;i<N;i+=4)

    {

        for(int j=5;j<N;j+=4)

        {

            int temp=i*j;

            if(temp>=N)

            break;

            if(ans[i]==0&&ans[j]==0)

            {

                ans[temp]=1;

            }

            else

            {

                ans[temp]=-1;

            }

        }

    }

    int sum=0;

    for(int i=1;i<N;++i)

    {

        if(ans[i]==1)

        ++sum;

        ans[i]=sum;

    }

}

int main()

{

    findans();

    int n;

    while(cin>>n)

    {

        if(n==0)

        break;

        cout<<n<<" "<<ans[n]<<endl;

    }

    return 0;

}