Largest Prime Divisor

#include <bits/stdc++.h>

using namespace std;
vector<long long>prime;
bitset<10000002>status;
void seive()
{
    long long i, j;
    for( i=4; i<10000002; i+=2) status[i]=1;
    for(i=3; i*i<=10000002; i+=2){
        if(status[i]==0){
            for(j=i*i; j<10000002; j+=2*i){
                status[j]=1;
            }
        }
    }
    for(i=2; i<10000002; i++){
        if(!status[i]){
            prime.push_back(i);
        }
    }
}
vector<int> mx;
int main()
{
    seive();
    long long n, c=0, m, root, i, ans=0;
    while(cin>>n && n){

    root=sqrt(n);
    ans=c=0;
    for(i=0; i<prime.size() && prime[i]*prime[i]<=n; i++){
        if(n%prime[i]==0){
            c++;
            while(n%prime[i]==0){
                n/=prime[i];
                ans=max(ans,prime[i]);
            }
        }
    }
    ans=max(ans,n);
    if(c<=1) cout<<-1<<endl;
    else cout<<ans<<endl;
    }
    return 0;
}