#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9;
const int MOD = INF+7;
const ll LINF = 1e18;
#define rep(i,N) for(int (i)=0;(i)<(N);++(i))
#define rrep(i,N) for(int (i)=(N-1);(i)>0;--i)
#define FOR(i,j,N) for(int (i)=(j);(i)<(N);++(i))
#define put(n) cout<<(n)<<endl;
#define all(v) v.begin(),v.end()
#define MP make_pair
#define pb(n) push_back(n)

std::vector<bool> is_prime(100001000,true);
std::vector<int> prime;

void SieveofEratosthenes(){
    prime.reserve(1000000);
    is_prime[0] = is_prime[1] = false;
    for(int i=2;i<=100000000;i+=2) is_prime[i] = false;
    for(int i=3;i<=100000000;i+=3) is_prime[i] = false;
    is_prime[2] = is_prime[3] = true;
    prime.push_back(2); prime.push_back(3);

    for(int i=5;i<=10000;++i){
        if(!is_prime[i]) continue;
        for(int j = i*2; j<=100000000;j*=2){
            is_prime[j] = false;
        }
        prime.push_back(i);
    }
}

int main(){
    SieveofEratosthenes();
    int N;
    cin >> N;
    for(int i=0;i<prime.size();++i){
        if(N % prime[i] == 0 && prime[i] != 2){
            cout << prime[i] << endl;
            return 0;
        }
    }
}