#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
template <class... T> void dbg(T... x) { char e{}; ((cerr << e << x, e = ' '), ...); }
template <class T> void org(T l, T r) { while (l != r) cerr << ' ' << *l++; cerr << '\n'; }
#define debug(x...) dbg(#x, '=', x, '\n')
#define olist(x...) dbg(#x, '='), org(x)
#else
#define debug(...) ((void)0)
#define olist(...) ((void)0)
#endif
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define ff first
#define ss second

using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using Pt = pair<int, int>;

template <class T> inline constexpr T inf = numeric_limits<T>::max() / 2;
constexpr int mod = 998244353;

template<class T> bool chmin(T &a, T b) { return (b < a and (a = b, true)); }
template<class T> bool chmax(T &a, T b) { return (a < b and (a = b, true)); }
template<class... T> int add(T... x) { int t{}; return (((t += x) %= mod), ...), t; }
template<class... T> int mul(T... x) { i64 t{1}; return (((t *= x) %= mod), ...), t; }

void solve() {
    i64 x;
    cin >> x;

    i64 p = *ranges::partition_point(views::iota(0ll, (i64)1e9 + 5), [&](i64 a) {
        return a * a < x;
    });

    if (p * p != x) {
        cout << -1 << '\n';
        return;
    }

    debug(p);

    bool f = true;
    const int kN = 1e6;
    vector<i64> val(kN + 1, 1);
    for  (i64 i = 2; i <= kN; i++) {
        for (i64 j = i; j <= kN; j += i) {
            if (val[j] < 0) continue;
            if (val[j] * (i128)i > (i128)2e18) {
                val[j] = -1;
            } else {
                val[j] *= i;
            }
        }
        
        if (p % i == 0) f = false;
        if (val[i] == p) {
            cout << i << '\n';
            return;
        }
    }

    if (f) cout << p << '\n';
    else cout << -1 << '\n';
    
}

signed main() {
    cin.tie(0)->sync_with_stdio(false);
    cin.exceptions(cin.failbit);
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}