static SinglyLinkedListNode mergeLists(SinglyLinkedListNode head1, SinglyLinkedListNode head2) {

         SinglyLinkedListNode newList = null;

    if(head1.data < head2.data){
        newList = new SinglyLinkedListNode(head1.data);
        head1 = head1.next;
    }else{
        newList = new SinglyLinkedListNode(head2.data);
        head2 = head2.next;
    }

    var head = newList;

    while(head1 != null && head2 != null){

        if(head1.data < head2.data){
            newList.next = new SinglyLinkedListNode(head1.data);
            head1 = head1.next;
        }else{
            newList.next = new SinglyLinkedListNode(head2.data);
            head2 = head2.next;
        }
        newList = newList.next;
    }
    newList.next = (head1 != null) ? head1 : head2;


    return head;
}