#include <iostream>
#include <cstdio>
#include <map>
#include <cstring>
using namespace std;

map<string, int> book;
int n, bnlen;
char ins[10], bookname[205];
int main() {
    cin >> n;

    while (n--) {
        scanf("%s", ins);
        gets(bookname);

        if (ins[0] == 'a') {
            book[bookname] = 1;
        } else {
            //if(book.count(bookname)){
            if (book.find(bookname) != book.end()) {
                cout << "yes" << endl;
            } else {
                cout << "no" << endl;
            }
        }
    }


}