#include <iostream>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int nz(int n)
{
    int s=0, p=5;
    while(p<=n)
    {
        s=s+n/p;
        p=p*5;
    }
    return s;
}

int main()
{
    int p, n, st, dr, mij, copie, ok=0;
    in>>p;
    st=1;
    dr=2000000000;
    while(st<=dr && ok==0)
    {
        mij=(st+dr)/2;
        int x=nz(mij);
        if(x==p)
        {
            copie=mij;
            ok=1;
        }
        else if(x<p)
        {
            st=mij+1;
        }
        else
            dr=mij-1;
    }
    if(ok==0)
        out<<-1;
    else
        out<<copie-(copie%5);
    return 0;
}