#include <bits/stdc++.h>
using namespace std ;
typedef long long ll ;
ll nr_cinci ( ll n )
{
    ll num = 0 ;
    while ( n )
    {
        num += n / 5 ;
        n /= 5 ;
    }
    return num ;
}
const ll MAX = 1e17 ;
int main ( )
{
    freopen ( "fact.in" , "r" , stdin ) ;
    freopen ( "fact.out" , "w" , stdout ) ;
    ll p ; cin >> p ;
    ll st = 1 , dr = MAX ;
    while ( st < dr )
    {
        ll mij = ( dr + st ) / 2 ;
        if ( nr_cinci ( mij ) < p ) st = mij + 1 ;
        else dr = mij ;
    }
    if ( nr_cinci ( st ) == p ) cout << st ;
    else cout << -1 ;
    return 0 ;
}