Lähetit

#!/usr/bin/env python3

# muokattu Metabolixin koodista

n, k = [int(x) for x in input().split()]

musta = [1, 2] + [0] * max(n, k)
for i in range(1, n - 1):
    lev = (i & ~1) + 2
    for j in range(min(k, lev), 0, -1):
        musta[j] += (musta[j - 1] * (lev - (j - 1))) % 1000000007

valk = [1, 1] + [0] * max(n, k)
for i in range(1, n):
    lev = (i & ~1) + 1
    for j in range(min(k, lev), 0, -1):
        valk[j] += (valk[j - 1] * (lev - (j - 1))) % 1000000007

ret = sum(musta[j] * valk[k - j] for j in range(0, min(n, k) + 1)) % 1000000007
print(ret if n > 1 else (1 if k <= n else 0))

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED