import UIKit

//struct Person {
//    var name: String
//    var surname: String
//    var age: Int
//
//    init(name: String, surname: String, age: Int) {
//        self.name = name
//        self.surname = surname
//        self.age = age
//    }
//}

class Person {
    ///feald
    var name: String
    private var surname: String
    var age: Int

    ///constructor
    init(name: String, surname: String, age: Int) {
        self.name = name
        self.surname = surname
        self.age = age
    }

    ///method
    func getSurname() -> String {
        return surname
    }
}

class Student: Person {
    var school: String
    var form: Int

    init(name: String, surname: String, age: Int, school: String, form: Int) {
        self.school = school
        self.form = form
        super.init(name: name, surname: surname, age: age)
    }
}

class GraduetingStrudent: Student {
    let numOfZNO: Int

    init(name: String, surname: String, age: Int, school: String, form: Int, numOfZNO: Int) {
        self.numOfZNO = numOfZNO
        super.init(name: name, surname: surname, age: age, school: school, form: form)
    }
}

let sKadir: Student = Student(name: "kadir", surname: "kadyrov", age: 20, school: "KNU", form: 3)




var world: [Person] = [Person]()

let kadir = Student(name: "Kadir", surname: "Kadyrov", age: 20, school: "KNU", form: 3)
let maxym = Student(name: "Maxym", surname: "Shymon", age: 20, school: "NAU", form: 3)
let p1 = Person(name: "p1", surname: "sp1", age: 10)
let gsTimur: GraduetingStrudent = GraduetingStrudent(name: "Timur", surname: "Krasnansky", age: 16, school: "171", form: 11, numOfZNO: 4)

world.append(kadir)
world.append(maxym)
world.append(p1)
world.append(gsTimur)

var x: Int? = nil
x = 10
//если в newx будет записан не nil то тело будет работать
if let newx = x {
    print("NO NIL \(newx)")
}

let p = world[0] as? Student
if let newKadir = p {
    print(newKadir.school)
}

//for i in 0...10 {
//
//}
//for i in 0..<10 {
//
//}

//for person in world {
//    if person as? Student != nil {
//
//    }
//}

var ans = 0

world.forEach { (elementOfWorld) in
    if elementOfWorld as? Student != nil && elementOfWorld as? GraduetingStrudent == nil {
        ans += 1
    }
}
print(ans)

//for i in 0..<world.count {
//    let person = world[i]
//    if world[i] as? Student != nil {
//
//    }
//}