//Q

// - add str
// - pop str


#include <iostream>
#include <string>
#include <unordered_set>

/*
add abcd  // (4)
add def   // (4, 3)
pop qwe   //
pop def
pop abcd

*/



int main() {
    std::unordered_set<std::string_view> words; // error, correct: std::string_view -> std::string
    std::string request;
    std::string word;
    while (std::cin >> request >> word) {
        if (request == "add") {
            words.insert(word);
        } else if (request == "pop") {
            std::unordered_set<std::string_view>::iterator it = words.find(word);
            if (it == words.end()) {
                std::cout << "NO\n";
            } else {
                std::cout << "YES\n";
                words.erase(it);
            }
        }
    }
}

std::set<int>::iterator it;
 ++it;
 --it;

std::advance(it, 10);
std::advance(it, -10);
std::distance(it, myset.end());

std::vector<int>::itearator it2;
it2 += 3;
it2 -= 4;