#include<bits/stdc++.h>
using namespace std;

#define n 20000005
bool mark[n+5]={false};
long long int isprime[n+5],i,j,k;
vector<long long int>v;

void sieve()
{
    mark[0]=true;
    mark[1]=true;

    for(i=2;i*i<=n;i+=2)
    {
        if(mark[i]==false)
        {
            for(j=i*i;j<=n;j+=i)
                mark[j]=true;
        }
    }
    k=0;
    for(i=2;i<=n;i++)
    {
        if(mark[i]==false)
            isprime[k++]=i;
    }
}

void solution(long long int a)
{
    long long int cnt=0;
    v.clear();
    for(i=0;isprime[i]*isprime[i]<=a;i++)
    {
        if(a%isprime[i]==0)
        {
            v.push_back(i);
            while(a%isprime[i]==0)
            {
                a/=isprime[i];
            }
        }
    }
    if(a!=1)
        v.push_back(a);
     //   sort(v.begin(),v.end());
    if(v.size()>1)
        cout<<v[v.size()-1]<<endl;
    else
        cout<<-1<<endl;
}

int main()
{
    sieve();
    long long int a;
    while(cin>>a && a)
    {
        if(a<0)
            a*=-1;
        solution(a);
    }
    return 0;
}