#include <cstdio>
using namespace std;

int main () {

    int p, k = 1, sw = -1;
    long long nr = 0, nract;

    FILE *in = fopen ("fact.in", "r");
    fscanf (in, "%d", &p);
    fclose (in);

    if (p == 0) {
        FILE *out = fopen ("fact.out", "w");
        fprintf (out, "1\n");
        fclose (out);
        return 0;
    }

    for (int i = 1; i <= p; ++i) {
        ++k;
        if (k == 6) {
            k = 0;
            nract = sw;
        }
        else {
            nr += 5;
            nract = nr;
        }
    }

    FILE *out = fopen ("fact.out", "w");
    fprintf (out, "%lld", nract);
    fclose (out);

    return 0;
}