#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <iomanip>
#include <assert.h>
#include <array>
#include <cstdio>
#include <cstring>
#include <random>
#include <functional>
#include <numeric>
#include <bitset>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)
#define all(c) (c).begin(), (c).end()
#define zero(a) memset(a, 0, sizeof a)
#define minus(a) memset(a, -1, sizeof a)
#define minimize(a, x) a = std::min(a, x)
#define maximize(a, x) a = std::max(a, x)

typedef long long ll;
int const inf = 1<<29;

int main() {
  ll N ;cin >> N;
  for(ll i=3; i*i<=N; i++) {
    if(N % i == 0) {
      cout << i << endl;
      exit(0);
    }
  }

  for(ll i=3; i<min(N, (ll)(1e8)); i++) {
    if(N % i == 0) {
      cout << i << endl;
      exit(0);
    }
  }

  if(N / 2 * 2 == N && N / 2 > 2) {
    N /= 2;
    for(ll i=2; i*i<=N; i++) {
      if(N % i == 0) {
        cout << i * 2 << endl;
        exit(0);
      }
    }
  }

  cout << N << endl;

  return 0;
}