#include <algorithm>
#include <iostream>
#include <vector>
#include <random>

using namespace std;

const int SIZE = 251;
const int FUNC = 50;

int64_t table[FUNC][SIZE];
vector<pair<int, int>> seed;

int get_hash(int id, int64_t a, int64_t b) {
    return (a + b * id) % SIZE;
}

int main() {
    int n;
    cin >> n;

    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<int> dist(100000, numeric_limits<int>::max());

    for (int i = 0; i < n; ++i) {
        int id, pay;
        cin >> id >> pay;

        for (int j = 0; j < FUNC; ++j) {
            int a = dist(gen);
            int b = dist(gen);
            seed.push_back({a, b});
            table[j][get_hash(id, a, b)] += pay;
        }
    }

    int card;
    cin >> card;
    int64_t ans = numeric_limits<int64_t>::max();

    for (int i = 0; i < FUNC; ++i) {

        int a = seed[i].first;
        int b = seed[i].second;
        int hash = get_hash(card, a, b);

        for (int j = 0; j < SIZE; ++j) {
            ans = min(ans, table[i][hash]);
        }
    }
    cout << ans << '\n';

}