#define ll long long

#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <math.h>

using namespace std;

int main() {
    int n, k;
    cin >> n >> k;

    if (n >= 5) {
        switch (k) {
            case 1:
                cout << 4;
                break;
            case 2:
                cout << 8;
                break;
            case 3:
                cout << 5;
                break;
        }
    } else {
        int a[5], b[5];
        a[0] = 1;
        b[0] = 1;
        for (int i = 1; i <= n; i++) {
            a[i] = a[i - 1] * i;
            b[i] = b[i - 1] * i;
        }

        for (int i = 2; i <= k; i++) {
            for (int j = 0; j <= n; j++) {
                a[j] *= (j == 0 ? 1 : b[j]);
            }
        }

        int sum = 0;
        for (int i = 0; i <= n; i++) {
            sum += a[i];
        }

        while (sum != 0) {
            if (sum % 10 != 0) {
                cout << sum % 10;
                break;
            }
            sum /= 10;
        }
    }
    return 0;
}