universal-dich

import kotlinx.atomicfu.AtomicRef;

public class Solution implements AtomicCounter {
    private final ThreadLocal<Node> last;

    public Solution(){
        this.last = new ThreadLocal<>();
    }

    public int getAndAdd(int x) {
        int res;
        while(true){
            int old = last.get().val.getValue();
            int upd = old;
            res = upd + x;
            ThreadLocal<Node> node = new ThreadLocal<>();
            node.get().val.setValue(upd);
            last.set(last.get().next.decide(node.get()));
            if (last.get() != node.get()){
                break;
            }
        }
        return res;
    }

    private static class Node {
        private final AtomicRef<Integer> val = new AtomicRef<>(0);
        private final Consensus<Node> next = new Consensus<>();
    }
}