急，不会，根本就没有思路，实在是搞不出来
def sum(a,b):
if b == 0 or a == b:
result = 1
return 1
return sum(a-1,b-1)+sum(a-1,b)
while True:
s = input()
n = int(s.split()[0])
m = int(s.split()[1])
print(sum(n,m))
def sum(a,b):
if b == 0 or a == b:
result = 1
return 1
return sum(a-1,b-1)+sum(a-1,b)
while True:
s = input()
n = int(s.split()[0])
m = int(s.split()[1])
print(sum(n,m))