#include <iostream>
#include <fstream>
#include <math.h>

using namespace std;

int fac(int a)
{
    int contor = 0,copie=a;
    while (copie / 10!=0)
    {
        copie = copie / 10;
        contor=contor*copie;
    }
    
    int nr_min;
   /* if (copie != 1)*/
    nr_min = (a - contor) * 5;



    return nr_min;
}

int main()
{
    ifstream f("fact.in");
    int a;
    f >> a;
    
    int abc = fac(a);



    ofstream g("fact.out");
    if (a < 0 || a>pow(10,8))
    
        g << -1;
    else
    {
     if (a == 0)
                g << 1;
            else
                g << abc;
    }
       
    
}