AB9 【模板】链表

var n =readline();
var item = []
for(let i = 0;i<n;i++)
    {
        let ls = readline().split(" ");
        if(ls.length ==2 && item.includes(ls[1])) 
            item.splice(item.indexOf(ls[1]),1);
        else if(ls.length ==2 && !item.includes(ls[1])) 
            continue;
        if(ls.length == 3 && item.includes(ls[1]))
            {
                item.splice(item.indexOf(ls[1]),0,ls[2])
            }
        else if(ls.length == 3 && !item.includes(ls[1]))
            {
                item.push(ls[2])
            }
    }
if(item.length == 0) console.log("NULL");
else {
    console.log(item.join(' '))

}