#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
long verificare(int n)
{
    long nr_zero;
    nr_zero=0;
    while(n/5)
    {
        nr_zero+=n/5;
        n/=5;
    }
    return nr_zero;
}
int main()
{
    long p;
    long mij,li=0,ls=32000;
    bool gasit;
    f>>p;
    while((li<=ls)&&(!gasit))
    {
        mij=(li+ls)/2;
    if(verificare(mij)==p&&verificare(mij-1)<p||mij<5)
        {
            if (mij<5)
                g<<"1";
            else
                g<<mij;
            gasit=1;
        }
    else
        if(verificare(mij)<p)
            li=mij+1;
        else ls=mij-1;
    }
if(gasit==0)
    g<<-1;
return 0;
}