#include <iostream>
#include <fstream>

#define in ifstream("fact.in")
#define out ofstream("fact.out")

using namespace std;

int x;

int countZeroes(int n)
{
    int counter = 0;

    for (int i = 5; n / i >= 1; i *= 5)
        counter += n / i;

    return counter;
}

int p = 0;

bool found(int n){
    for(int i = n; i<=n*5;++i){
        if(n == countZeroes(i)){
            p = i;
            return true;
            break;
        }
    }
    return false;
}

int main()
{
    in >> x;

    if(x == 0){
        out << 1 << '\n';
    } else {
        if(found(x) == true){
            out << p << '\n';
        } else {
            out << -1 << '\n';
        }
    }

}