#include <iostream>
#include <fstream>
using namespace std;
int verf(int n)
{
    int rez=0;
    while(n)
    {
        rez=rez+n/5;
        n=n/5;
    }
    return rez;
}
int main()
{
ifstream f("fact.in");
ofstream g("fact.out");
int p,i,gasit=0,nr=1,x;
f>>p;
while(gasit==0)
{
    nr++;
    if(verf(nr)==p)
    {
        x=nr;
        gasit=1;
    }


}
if(gasit==1)
    g<<x;
else
    g<<-1;


    return 0;
}