class Shape {
    public lineCount: number

    constructor(lineCount: number) {
        this.lineCount = lineCount
    }
}

class Square extends Shape {
    public sideLength: number

    constructor(sideLength: number) {
        super(4)
        this.sideLength = sideLength
    }
}

let square = new Square(5)
console.log("lineCount is", 
    square.lineCount)
console.log("sideLength is",
    square.sideLength)