#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
#define ll long long
int zeros(int n)
{
    ll nr=0,p=5;
    while(p<=n)
    {
        nr+= (n / p);
        p*=5;
    }
    return nr;
}

int cb(int n)
{
    ll st=1 , dr=1e9 , sol=-1;
    while(st<=dr)
    {
        ll mij = (st+dr)/2;
        if(zeros(mij)==n)
        {
            sol=mij;
            dr=mij-1;
        }
        else if(zeros(mij)>n)
            dr=mij-1;
        else
            st=mij+1;
    }
    return sol;
}

int main()
{
    ll n;
    fin>>n;
    fout<<cb(n);
    return 0;
}