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// 手写拉链
#include <vector>
#include <string>
#include <iostream>
const int MAX = 1e5 + 10;
const int HASH = 1e7 + 7;
const int OFFSET = 2e9 + 5;
const int A = 263, B = 997;
#define hash(x) ((((263*1LL*((x%OFFSET+OFFSET)%OFFSET)+997)%HASH+HASH)%HASH)%MAX)
#define insert(x) hash_table[hash(x)].emplace_back(x)

std::vector<int> hash_table[MAX];

bool find(int x) {
    for (auto a : hash_table[hash(x)])
        if (a == x) return true;
    return false;
}

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    int N, x; std::string op;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") insert(x);
        else std::cout << (find(x) ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// STL unordered_map
#include <string>
#include <iostream>
#include <unordered_map>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    int N, x; std::string op;
    std::unordered_map<int, int> set;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set[x] = 1;
        else std::cout << (set[x] ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// STL map
#include <map>
#include <string>
#include <iostream>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    int N, x; std::string op;
    std::map<int, int> set;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set[x] = 1;
        else std::cout << (set[x] ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// STL set
#include <set>
#include <string>
#include <iostream>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    int N, x; std::string op;
    std::set<int> set;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set.insert(x);
        else std::cout << (set.find(x) != set.end() ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// pb_ds gp_hash_table
#include <string>
#include <iostream>
#include <bits/extc++.h>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    __gnu_pbds::gp_hash_table<int, int> set;
    int N, x; std::string op;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set[x] = 1;
        else std::cout << (set[x] ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// pb_ds cc_hash_table
#include <string>
#include <iostream>
#include <bits/extc++.h>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    __gnu_pbds::cc_hash_table<int, int> set;
    int N, x; std::string op;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set[x] = 1;
        else std::cout << (set[x] ? "Yes\n" : "No\n");
    }
    std::cout.flush();
    return 0;
}

// STL std::unordered_set
#include <iostream>
#include <string>
#include <unordered_set>

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    int N; std::string op; int x;
    std::unordered_set<int> set;
    for (std::cin >> N; N; --N) {
        std::cin >> op >> x;
        if (op == "I") set.insert(x);
        else std::cout << (set.find(x) == set.end() ? "No\n" : "Yes\n");
    }
    std::cout.flush();
    return 0;
}

实测 __gnu_pbds::gp_hash_table 是最快的