n = int(input("Podaj n: "))
k = int(input("Podaj k: "))
B = [[i * j for i in range(n)] for j in range(k)]
def f(n, k):
for i in range(n):
for j in range(k):
if i==0 and j==0:
B[i][j] = 1
if i==0:
B[i][j]= 0
if i==j and i!=0:
B[i][j] = 2
if i!=0 and j!=0 and i!=j:
B[i][j] = i * B[i-1][j] + j * B[i-1][j-1]
f(n, k)
print(B[n][k])