task 7 (fnc)

def A(a, b) -> int:
    if a > b:
        return 0
    if a == b:
        return 1
    if a == 29 or a == 39 or a == 49:
        return A(a+1, b) + A(a+10, b)
    return A(a+1,b) + A(a+11, b)
print(A(25, 51))