#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <deque>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define p(s) cout<<(s)<<endl
#define REP(i,n,N) for(int i=n;i<N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=n;i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;

ll N,ans;
vector<int> hurui_v(int n) {
    vector<int> v;
    bool *isPrime_v;
    isPrime_v = new bool[n + 1]; // 処理用のメモリ確保

    // 初期化
    isPrime_v[0] = isPrime_v[1] = isPrime_v[2] = false;
    for (int i = 3; i < n + 1; i++) isPrime_v[i] = true;

    // isPrime[0~n]で素数のものだけtrueにする
    for (int i = 3; i*i <= n; i++) {
        for (int j = i * 2; j < n + 1; j += i) {
            isPrime_v[j] = false;
        }
    }

    // 素数のみ追加
    for (int i = 0; i < n + 1; i++) {
        if (isPrime_v[i]) v.push_back(i);
    }

    delete[] isPrime_v; //メモリ解放
    return v;
}

int main(){
    cin>>N;
    vector<int> prime = hurui_v(1e6);
    for(auto pr:prime){
        if(N%pr==0){
            ans=pr;
            break;
        }
        if(N<=pr*pr){
            ans=N;
            break;
        }
    }
    p(ans);
    return 0;
}