#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 int MAX = 1e17 ;
int main ( )
{
    freopen ( "fact.in" , "r" , stdin ) ;
    freopen ( "fact.out" , "w" , stdout ) ;
    ll p ; cin >> p ;
    ll index = 0 ;
    for ( int bit = 17 ; bit >= 0 ; bit -- )
    {
        index += ( 1 << bit ) ;
        if ( nr_cinci ( index ) > p - 1 ) index -= ( 1 << bit ) ;
    }
    cout << index + 1 ;
    return 0 ;
}