count = 0
def choose(n,k):
global count
count += 1
if k <= 0:
return 1
elif n < k:
return 0
else:
return choose(n-1, k-1) + choose(n-1, k)
print "answer: ", choose(500,2)
print "function calls: ", count
Y291bnQgPSAwCgpkZWYgY2hvb3NlKG4sayk6CglnbG9iYWwgY291bnQKCWNvdW50ICs9IDEKCWlmIGsgPD0gMDoKCQlyZXR1cm4gMQoJZWxpZiBuIDwgazoKCQlyZXR1cm4gMAoJZWxzZToKCQlyZXR1cm4gY2hvb3NlKG4tMSwgay0xKSArIGNob29zZShuLTEsIGspCgpwcmludCAiYW5zd2VyOiAiLCBjaG9vc2UoNTAwLDIpCnByaW50ICJmdW5jdGlvbiBjYWxsczogIiwgY291bnQ=