m,n=map(int,input().split()) lt=[[0 for i in range(n+1)]for i in range(m+1)] lt[-2][1]=1 for i in range(-1,-1*m): for j in range(1,n): lt[i][j]=lt[i][j-1]+lt[i-1][j-1] print(lt) print(lt[0][-1]) 哪里错?