fn base58(c: u8) -> Bool {
    if c >= 49 && c <= 57 {
        return c != 48
    }
    if c >= 65 && c <= 90 {
        return c != 73 && c != 79
    }
    if c >= 97 && c <= 122 {
        return c != 108
    }
    return false
}

pub fn main(world: World) -> Void raises {
    if base58(49) && !base58(48) {
        check world.out.write("bitcoin address ok\n")
    }
}