Bit Strings

import sys

sys.setrecursionlimit(1000000)

n, k = [int(x) for x in input().split()]

def add_nr(zs, ln=0, cache = {}):
	global l
	if ln == n:
		return 1
	if (zs, ln) not in cache:
		if zs != k - 1:
			cache[(zs, ln)] = add_nr(zs + 1, ln + 1) + add_nr(0, ln + 1)

		else:
			cache[(zs, ln)] = add_nr(0, ln + 1)
	return cache[(zs, ln)]

print(add_nr(0))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: RUNTIME ERROR

Test 12

Verdict: RUNTIME ERROR

Test 13

Verdict: RUNTIME ERROR

Test 14

Verdict: RUNTIME ERROR

Test 15

Verdict: RUNTIME ERROR

Test 16

Verdict: RUNTIME ERROR

Test 17

Verdict: RUNTIME ERROR

Test 18

Verdict: RUNTIME ERROR