#include <iostream>
#include <cstdio>
using namespace std;

long long numarzero(int n)
{
    long long nr=0;
    while(n!=0)
    {
        nr=nr+n/5;
        n=n/5;
    }
    return nr;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    long long P; cin>>P;
    long long m,u,p;
    p=1;
    u=5*P;
    while (p<=u)
    {
        m = p+(u-p)/2;
        if (numarzero(m)>=P)
            u = m-1;
        else
            p = m+1;
    }
    int copie=p;
    while(copie%5==0)
        copie=copie/5;
    if(copie==1&&p!=1)
        cout<<-1;
    else
        cout<<p;

    return 0;
}