struct base_user:
    health: i32 = 100

virtual func (u base_user) take_damage(amount: i32):
    u.health -= amount

struct player extends base_user:
    armor: i32

override func (p player) take_damage(amount: i32):
    super.take_damage(amount)
    p.armor++

func apply(u: base_user):
    u.take_damage(3)

func entry(value: i32) -> i32:
    var p = player(armor = value)
    var b: base_user = p
    apply(b)
    if b == p:
        return b.health + p.armor
    return 0