
https://www.acmicpc.net/problem/1010

import sys
def fac(n):
if n < 2:
return 1
else:
return n * fac(n-1)
t = int(sys.stdin.readline())
for i in range(t):
n,m = map(int, sys.stdin.readline().split())
print(fac(m) // (fac(m-n) * fac(n)))```