#include<bits/stdc++.h>
#define EM 1000000
using namespace std;
using LL = long long;
using P = pair<LL, LL>;
LL LINF = 1e18;
int INF = 1e9;
LL mod = 1e9+7;
using vint = vector<int>;
using vLL = vector<LL>;
using vvint = vector<vector<int>>;
using vvLL = vector<vector<LL>>;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

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