#include <bits/stdc++.h>
/*
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,fma,abm,mmx,avx,avx2")
*/
#define rep(i, n) for (ll i = 0; i < (int)(n); i++)
#define rrep(i, n) for (ll i = (int)(n) - 1; i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ll(x.size())
#define yn(joken) cout<<((joken) ? "Yes" : "No")<<"\n"
#define YN(joken) cout<<((joken) ? "YES" : "NO")<<"\n"
#define UNIQUE(x) sort(all(x)), x.erase(unique(all(x)), x.end())
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vpi = vector<pair<int,int>>;
using vpl = vector<pair<ll,ll>>;
using vs = vector<string>;
using vc = vector<char>;
using vd = vector<double>;
using vld = vector<long double>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvs = vector<vector<string>>;
using vvc = vector<vector<char>>;
using vvd = vector<vector<double>>;
using vvld = vector<vector<long double>>;
using vvvi = vector<vector<vector<int>>>;
using vvvl = vector<vector<vector<ll>>>;
using vvvvi = vector<vector<vector<vector<int>>>>;
using vvvvl = vector<vector<vector<vector<ll>>>>;
template <class T> using priq = priority_queue<T>;
template <class T> using priqg = priority_queue<T, vector<T>, greater<T>>;
const int INF = 1e9;
const ll LINF = 2e18;
template <class T, class S> inline bool chmax(T &a, const S &b) { return (a < b ? a = b, 1 : 0); }
template <class T, class S> inline bool chmin(T &a, const S &b) { return (a > b ? a = b, 1 : 0); }
vi iota(int n) {
    vi a(n);
    return iota(a.begin(), a.end(), 0), a;
}
template <typename T> vi iota(const vector<T> &a, bool greater = false) {
    vi ret(a.size());
    iota(ret.begin(), ret.end(), 0);
    sort(ret.begin(), ret.end(), [&](int i, int j) {
        if(greater) return a[i] > a[j];
        return a[i] < a[j];
    });
    return ret;
}
template <typename S> void rearrange(const vector<S> &id) {}
template <typename S, typename T> void rearrange_exec(const vector<S> &id, vector<T> &v) {
    vector<T> w(v.size());
    rep(i, sz(id)) w[i] = v[id[i]];
    v.swap(w);
}
// 並び替える順番, 並び替えるvector
template <typename S, typename Head, typename... Tail> void rearrange(const vector<S> &id, Head &a, Tail &...tail) {
    rearrange_exec(id, a);
    rearrange(id, tail...);
}
template <typename T> vector<T> RUI(const vector<T> &v) {
    vector<T> res(v.size() + 1);
    for(int i = 0; i < v.size(); i++) res[i + 1] = res[i] + v[i];
    return res;
}
// 反時計周りに 90 度回転
template <typename T> void roth(vector<vector<T>> &v) {
    if(empty(v)) return;
    int n = v.size(), m = v[0].size();
    vector<vector<T>> res(m, vector<T>(n));
    rep(i, n) rep(j, m) res[m - 1 - j][i] = v[i][j];
    v.swap(res);
}
// 時計周りに 90 度回転
template <typename T> void rott(vector<vector<T>> &v) {
    if(empty(v)) return;
    int n = v.size(), m = v[0].size();
    vector<vector<T>> res(m, vector<T>(n));
    rep(i, n) rep(j, m) res[j][n - 1 - i] = v[i][j];
    v.swap(res);
}
bool ispow2(int i) { return i && (i & -i) == i; }
bool ispow2(ll i) { return i && (i & -i) == i; }
template <typename T, typename S> T ceil(T x, S y) { // x/y以上の最小の整数を返す
    assert(y);
    return (y < 0 ? ceil(-x, -y) : (x > 0 ? (x + y - 1) / y : x / y));
}
 
template <typename T, typename S> T floor(T x, S y) { // x/y以下の最大の整数を返す
    assert(y);
    return (y < 0 ? floor(-x, -y) : (x > 0 ? x / y : x / y - (x % y == 0 ? 0 : 1)));
}
template <class S> vector<pair<S, int>> RunLength(const vector<S> &v) {
    vector<pair<S, int>> res;
    for(auto &e : v) {
        if(res.empty() || res.back().first != e)
            res.emplace_back(e, 1);
        else
            res.back().second++;
    }
    return res;
}
vector<pair<char, int>> RunLength(const string &v) {
    vector<pair<char, int>> res;
    for(auto &e : v) {
        if(res.empty() || res.back().first != e)
            res.emplace_back(e, 1);
        else
            res.back().second++;
    }
    return res;
}
template <class T, class F> T bin_search(T ok, T ng, const F &f) {
    while(abs(ok - ng) > 1) {
        T mid = ok + ng >> 1;
        (f(mid) ? ok : ng) = mid;
    }
    return ok;
}
template <class T, class F> T bin_search_double(T ok, T ng, const F &f, int iter = 80) {
    while(iter--) {
        T mid = (ok + ng) / 2;
        (f(mid) ? ok : ng) = mid;
    }
    return ok;
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        is >> v[i];
    }
    return is;
}
namespace aux {
template <typename T, unsigned N, unsigned L> struct tp {
    static void output(std::ostream &os, const T &v) {
        os << std::get<N>(v) << (&os == &cerr ? ", " : " ");
        tp<T, N + 1, L>::output(os, v);
    }
};
template <typename T, unsigned N> struct tp<T, N, N> {
    static void output(std::ostream &os, const T &v) { os << std::get<N>(v); }
};
} // namespace aux
template <typename... Ts> std::ostream &operator<<(std::ostream &os, const std::tuple<Ts...> &t) {
    if(&os == &cerr) { os << '('; }
    aux::tp<std::tuple<Ts...>, 0, sizeof...(Ts) - 1>::output(os, t);
    if(&os == &cerr) { os << ')'; }
    return os;
}
template <typename T> std::ostream &operator<<(std::ostream &os, const stack<T> &_st) {
    auto st = _st;
    vector<T> res;
    while(!empty(st)) res.emplace_back(st.top()), st.pop();
    reverse(all(res));
    return os << res;
}
template <typename T> std::ostream &operator<<(std::ostream &os, const queue<T> &_qu) {
    auto qu = _qu;
    vector<T> res;
    while(!empty(qu)) res.emplace_back(qu.front()), qu.pop();
    return os << res;
}
template <typename T> std::ostream &operator<<(std::ostream &os, const deque<T> &_dq) {
    auto dq = _dq;
    vector<T> res;
    while(!empty(dq)) res.emplace_back(dq.front()), dq.pop_front();
    return os << res;
}
template <typename T, typename S, typename U> std::ostream &operator<<(std::ostream &os, const priority_queue<T, S, U> &_pq) {
    auto pq = _pq;
    vector<T> res;
    while(!empty(pq)) res.emplace_back(pq.top()), pq.pop();
    return os << res;
}
template <class T, class S> ostream &operator<<(ostream &os, const pair<T, S> &p) {
    if(&os == &cerr) { return os << "(" << p.first << ", " << p.second << ")"; }
    return os << p.first << " " << p.second;
}
template <class Ch, class Tr, class Container> std::basic_ostream<Ch, Tr> &operator<<(std::basic_ostream<Ch, Tr> &os, const Container &x) {
    bool f = true;
    if(&os == &cerr) os << "[";
    for(auto &y : x) {
        if(&os == &cerr)
            os << (f ? "" : ", ") << y;
        else
            os << (f ? "" : " ") << y;
        f = false;
    }
    if(&os == &cerr) os << "]";
    return os;
}

static uint32_t RandXor(){
    static uint32_t x=123456789;
    static uint32_t y=362436069;
    static uint32_t z=521288629;
    static uint32_t w=88675123;
    uint32_t t;
 
    t=x^(x<<11);
    x=y; y=z; z=w;
    return w=(w^(w>>19))^(t^(t>>8));
}

static double Rand01(){
    return (RandXor()+0.5)*(1.0/UINT_MAX);
}

template <typename T>
void rshuffle(vector<T> &V){
    random_device seed_gen;
    mt19937 engine(seed_gen());
    shuffle(V.begin(),V.end(),engine);
}

void solve(){
    ll N;
    cin>>N;
    ll ans=N;
    for(ll i=3;i*i<=N;i++) if(N%i==0) chmin(ans,i);
    if(N%2==0 && N/2>2) chmin(ans,N/2);
    cout<<ans<<"\n";
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();
}