Uva 11466 - Largest Prime Divisor

 // 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>
#include<cstdlib>
// End
//..........
// Macro
#define sf scanf
#define pf printf
#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<<" "
#define nl puts("")
#define sq(x) ((x)*(x))
#define all(x) x.begin(),x.end()
#define reall(x) x.rbegin(),x.rend()
#define sz size()
#define gc getchar()
#define pb push_back
#define freader freopen("input.txt","r",stdin)
// 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 (65540)
#define mod 1000000007
#define pi acos(-1.0)

// Macros for Graph

#define white 1
#define gray 2
#define black 3
#define nil 0

using namespace std;
/***************/

// typedef

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;
typedef vector<int>vi;
typedef vector<long long> vll;
typedef vector<long>vl;
typedef vector<char>vch;
typedef vector<string>vs;
typedef map<int,int>mpii;
typedef map<int,bool>mpbi;
typedef map<long,bool>mpbl;
typedef map<long long,bool>mpbll;
typedef map<char,int>mpci;
typedef map<char,bool>mpbc;
typedef map<string,int>mpsi;
typedef map<long long,long long>mpll;

// template

template<class T> T gcd(T a, T b ) {return b!=0?gcd<T>(b,a%b):a;}
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[(mx4>>6)+1],prm[(mx4>>1)+9],plen=0,qrt=(int)sqrt(double(mx4));

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

void sieve()
{
    int i,j;
    for(i=3;i<=qrt;i+=2)
    {
        if(!checkbit(i))
        {
            for(j=i*i;j<=mx4;j+=i+i)
            {
                setbit(j);
            }
        }
    }
    prm[plen++]=2;

    for(i=3;i<=mx4;i+=2)
    {
        if(!checkbit(i))
        {
            prm[plen++]=i;
        }
    }

    //lp1(i,100)cp(prm[i]);
}

mpbll mp;

LL facto(LL n)
{
    mp.clear();
    LL i,cnt=0;
    LL maxi = -1;
    for(i=0;i<plen and sq(prm[i])<=n;i++)
    {
        if(!(n%prm[i]))
        {
            while(!(n%prm[i]))
            {
                n/=prm[i];
                if(n==0 or n==1)break;
            }

            if(!mp[prm[i]])
            {
                cnt++;
                if(maxi < prm[i])
                {
                    maxi = prm[i];
                }

                mp[prm[i]] = true;
            }
        }
    }

    if(n>1)
    {
        if(!mp[n])
        {
            cnt++;
            if(maxi < n)
            {
                maxi = n;
            }
            mp[n]=true;
        }
    }

    if(cnt <= 1)
    {
        return -1;
    }

    else
    {
        return maxi;
    }
}

int main()
{
    sieve();
    LL num;
    while(~sf("%lld",&num) and num)
    {
        if(num<0)num*=-1;
        pf("%lld\n",facto(num));
    }

    return 0;
}