class NumberNode {
    public data: number;
    public next: NumberNode;
    
    public constructor(data: number) {
        this.data = data;
    } 
}
class SLList {
    private head: NumberNode;
    
    public push(data: number) {
        const node = new NumberNode(data);
        node.next = this.head;
        this.head = node;
    }
}

const list = new SLList();
list.push(3);
list.push(2);
list.push(1);
console.log(list);