Codeforces Round #326 (Div. 2), problem: (B) Duff in Love

#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define pii pair<int,int>
#define pli pair<long long int,int>
#define pbi pair<bool,int>
#define pob pop_back
#define all(a) a.begin(),a.end()
#define fio ios_base::sync_with_stdio(false); cin.tie(NULL);cout.tie(NULL);
#define i64 long long int
#define mem(x,y) memset(x,y,sizeof(x))
#define fill(arr,b) fill(arr, arr+sizeof(arr)/sizeof(arr[0]), b)
#define maxarr(n,arr,m) m=-1e9;for(int i=0;i<n;i++)if(arr[i]>m) m=arr[i];
#define read freopen("input.txt","r",stdin);
#define F first
#define S second

const int maxn = (i64)1e9+7;
const double pi = acos(-1.0);

//bool fne(const pii &a, const pii &b){return (a.F < b.F)||(a.F==b.F&&a.S<b.S);}
//bool sne(const pii &a, const pii &b){return (a.S < b.S)||(a.S==b.S&&a.F<b.F);}
vector<int>v;
const int N=1000005;
int pr[N+1],k=1;
int lp[N+1];
int f(i64 n)
{
    for (int i=2; i<=n+5; ++i)
    {
        if (lp[i] == 0){lp[i] = i;pr[k++] = i;}
        for (int j=1; j<k && pr[j]<=lp[i] && i*pr[j]<=n; ++j)
            lp[i * pr[j]] = pr[j];
    }
return 0;
}

int main()
{
    //read;
    fio;
    i64 n;
    cin>>n;
    i64 x=n;
    f(sqrt(n));
    i64 ans=1;
    //cout<<k;
    for(int i=1;1LL*pr[i]*pr[i]<=x;i++)
    {
        if(n%pr[i]==0)
        {
            ans*=pr[i]*1LL;
            while(n%pr[i]==0) n/=pr[i];
        }
    }
    if(n>1) ans*=n;
    cout<<ans;
    return 0;
}