from itertools import permutations
n,r=map(int,input().split())#ball:n   basket:r
l=[chr(i) for i in range(97,97+n)]
ls=[]
for i in range(1,n-r+2):
    v=list(permutations(l,i))
    ls.append(v)
for m in range(len(ls)):
    for z in range(len(ls[m])):
        if len(ls[m][z]) > 1:
            for w in range(z+1,len(ls[m])):
                if ls[m][z][0]==ls[m][w][1] and ls[m][z][1]==ls[m][w][0]:
                    ls[m][z]=[0]
                    break
        else:
            break
ans=0
for q in ls:
    for u in q:
        if u!=[0]:
            ans+=1
print(ans)

不知道代码问题出在哪，我的思路是转成字符存起来在符合条件的情况下计算全排列再去重