#include <iostream>
#include <fstream>

using namespace std;

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

int n;

int rez (int x) {
    int zerouri = 0;

    while (x >= 5) {
        zerouri += x / 5;
        x /= 5;
    }
    return zerouri;
}

int caut () {
    int i = 0, p = 1 << 30;
    while (p) {
        if (rez (i + p) < n) i = i + p;
        p = p >> 1;
    }
    return i + 1;
}

int main () {
    f >> n;
    int sol = caut ();
    if (rez (sol) == n) g << sol << '\n';
    else g << "-1\n";
    return 0;
}