A permutation *p* of size *n* is an array such that every integer from 1 to *n* occurs exactly once in this array.

Let's call a permutation an almost identity permutation iff there exist at least *n* - *k* indices *i* (1 ≤ *i* ≤ *n*) such that *p*<sub class="lower-index">*i*</sub> = *i*.

Your task is to count the number of almost identity permutations for given numbers *n* and *k*.
The first line contains two integers *n* and *k* (4 ≤ *n* ≤ 1000, 1 ≤ *k* ≤ 4).
none
4 1
1
4 2
7
5 3
31
5 4
76
200 1
1
200 2
19901
200 3
2646701
200 4
584811251
400 1
1
400 2
79801
400 3
21253401
400 4
9477912501
600 1
1
600 2
179701
600 3
71820101
600 4
48187303751
800 1
1
800 2
319601
800 3
170346801
800 4
152620985001
1000 1
1
1000 2
499501
1000 3
332833501
1000 4
373086956251
4 4
24
import itertools

def C(n, m):
    ret = 1
    for i in range(m):
        ret *= (n - i)
    for i in range(m):
        ret //= (i + 1)
    return ret

n, k = map(int, input().split())
d = [0] * (k + 1)

for m in range(k + 1):
    p = list()
    for i in range(m):
        p.append(i)
    pp = itertools.permutations(p)
    for permutation in pp:
        ok = True
        for i in range(m):
            if permutation[i] == i:
                ok = False
                break
        if ok: d[m] += 1

ans = 0
for m in range(k + 1):
    ans += C(n, m) * d[m]
print(ans)