#include<iostream>
#include<fstream>
using namespace std;
int main()
{
    long long n=5,nr,p,aux;
    fstream f("factorial.in");
    ofstream g("factorial.out");
    while(f>>p)
    {
        if(p==0)
            g<<1<<endl;
        if(p<0)
            g<<-1<<endl;
        n=0;
        while(p>0)
        {
            nr=0;
            n+=5;
            aux=n;
            while(aux%5==0)
            {
                aux/=5;
                nr++;
            }
            p-=nr;
        }
        if(n>0)
           {
               aux=n;
               if(p<0)
                  aux=-1;
               g<<aux<<endl;}

   }
    return 0;
}