public class Pair<K,V>{
    K key;
    V value;
    public Pair(K key,V value){
        this.key=key;
        this.value=value;
    }
    public K getkey(){
        return key;
    }
    public V getvalue(){
        return value;
    }
    public static Pair swap (Pair pair){
        return new Pair(pair.getvalue(),pair.getkey());

    }
}