#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int solve(int p) {
    int n = 1;
    int c0 = 0;

    while (c0 != p && n <= 1000000) {
        int f = n;

        while (f % 5 == 0) {
            c0++;
            f /= 5;
        }

        n++;
    }

    if (c0 == p) {
        return n - 1;
    }
    else {
        return -1;
    }
}

int main() {

    int p;

    fin >> p;

    int sol = solve(p);

    fout << sol << '\n';


    return 0;
}