#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
typedef unsigned long long ull ;
typedef pair < int , int > pii ;
typedef vector < int > vi ;
#define fi first
#define se second
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()


ll n ;

ll calc_val ( ll x , ll pw ) {
    ll ret = 1 ;
    for ( int i = 1 ; i <= pw ; ++ i ) {
        if ( ret > n / x ) { return n + 1 ; }
        ret *= x ;
    }
    return ret ;
}

ll get ( ll pw ) {
    ll l , r , mid ;
    l = 1 , r = n ;
    while ( l < r ) {
        mid = ( l + r + 1 ) / 2 ;
        ll sr = calc_val ( mid , pw ) ;
        if ( sr <= n ) { l = mid ; }
        else { r = mid - 1 ; }
    }
    if ( calc_val ( l , pw ) == n ) { return l ; }
    return -1 ;
}

ll divs ( ll x ) {
    ll ret = 1 ;
    for ( ll i = 2 ; i * i <= x ; ++ i ) {
        if ( ( x % i ) == 0 ) {
            ll coef = 1 ;
            while ( ( x % i ) == 0 ) {
                x /= i ;
                ++ coef ;
            }
            ret = ( ret * coef ) ;
        }
    }
    if ( x > 1 ) { ret *= 2 ; }
    return ret ;
}

void solve ( ) {
    cin >> n ;
    if ( n == 1 ) {
        cout << "1\n" ;
        return ;
    }
    for ( ll pw = 62 ; pw >= 2 ; -- pw ) {
        ll aux = get ( pw ) ;
        if ( aux != -1 && divs ( aux ) == pw ) {
            cout << aux << "\n" ;
            return ;
        }
    }
    cout << "-1\n" ;
}

int main ( ) {
    ios_base :: sync_with_stdio ( false ) ;
    cin.tie ( NULL ) ;
    int t = 1 ; // cin >> t ;
    while ( t -- ) { solve ( ) ; }
    return 0 ;
}