#include<iostream>
#include<algorithm>
#include<vector>
#include<cmath>
#include<memory>
using namespace std;
using Long=long long int;

std::vector<Long> genprimes(Long N) {
    std::vector<Long> p(N);
    for(Long i=2;i<N;++i) p[i]=i;
    for(Long i=2;i<sqrt(N);++i) {
        if(p[i]) {
            for(Long j=2*i;j<N;j+=i) {
                p[j]=0;
            }
        }
    }
    p.erase(remove(p.begin(),p.end(),0),p.end());
    return p;
}

bool isprime(Long N) {
    if(N<2) return false;
    if(N==2||N==3)return true;
    if(N%2==0||N%3==0)return false;
    for(Long i=6;i<sqrt(N)+1;i+=6) {
        if(N%(i-1)==0 || N%(i+1)==0) return false;
    }
    return true;
}

int main() {
    auto primes = genprimes(Long(1e6));
    Long N;cin>>N;
    if(N%2==0 || N%3==0) {
        if(N%3==0) {
            cout << 3 << endl; return 0;
        }
        else if (N%4==0) {
            cout << 4 << endl; return 0;
        }
        else if(isprime(N/2)) {
            cout << N/2 << endl; return 0;
        }
    }

    for(auto x : primes) {
        if(x==2) continue;
        if(N%x==0) {
            cout<<x<<endl;
            return 0;
        }
    }
    cout<<N<<endl;
}