25 lines
465 B
Python
25 lines
465 B
Python
f = open('INPUT.TXT')
|
|
n, m = map(int, f.readline().split())
|
|
f.close()
|
|
|
|
def factorial(x):
|
|
if x <= 1:
|
|
return 1
|
|
result = 1
|
|
for i in range(2, x + 1):
|
|
result = result * i
|
|
return result
|
|
|
|
def binomial(n, k):
|
|
if k > n or k < 0:
|
|
return 0
|
|
return factorial(n) // (factorial(k) * factorial(n - k))
|
|
|
|
count = 0
|
|
for k in range(m, n + 1):
|
|
count = count + binomial(n, k)
|
|
|
|
f = open('OUTPUT.TXT', 'w')
|
|
f.write(str(count))
|
|
f.close()
|