j1_02.py

def solve(n, k):
    dx = [ 1, 0, -1, 0]
    dy = [ 0,-1,  0, 1]
    def move(x, y, d):
        if x == k and y == n - k: return 1
        if d == 0: return 0
        sol = 0
        for i in range(4):
            sol += move(x + dx[i], y + dy[i], d - 1)
        return sol
    return move(0, 0, n)