#include <iostream>
#include <fstream>

using namespace std;

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

long long n, p;

int ZeroSf(int x)
{
    int nr = 0;
    while(x)
    {
        nr += x/5;
        x/=5;
    }
    return nr;
}

int cauta(int st, int dr)
{
    int mid, sol = -1;
    for(int i = st;i <=dr;i++)
        if(ZeroSf(i)==n)
            return i;
    return sol;
}

int main()
{
    cin>>n;
    if(n!=0)
        cout<<cauta(n/5, n*5);
    else cout<<1;
}