#include <iostream>
#include <string>
#include <vector>
#include <set>
#include <cmath>
#include <algorithm>
#include <iomanip>
using ll = long long;
using namespace std;
#define MAX 10000000000000
int main(void)
{
    ll N;
    cin >> N;
    ll minV= MAX;
    if(N!=4&&N%2==0){
        minV = N/2;
    }
    
    for (ll i = 3; i * i <= N; ++i)
    {
        if (N % i == 0)
        {
            cout << i << endl;
            return 0;
        }
    }
    cout << min(minV, N) << endl;
    return 0;
}