Untitled

#include <iostream>
#include <queue>
#include <set>
#include <vector>

using namespace std;

int main() {
    int N, rackSize;
    cin >> N;

    vector<int> demands(N);
    for(int i = 0; i < N; i++) {
        cin >> demands[i];
    }

    cin >> rackSize;

    queue<int> rack; // Represents the current CDs on the rack in order
    set<int> rackSet; // Used for quick lookup to see if a CD is on the rack

    int misses = 0;

    for(int i = 0; i < N; i++) {
        if(rackSet.find(demands[i]) == rackSet.end()) { // CD is not on the rack
            misses++;

            if(rack.size() == rackSize) { // Rack is full, need to remove a CD
                int removedCd = rack.front();
                rack.pop();
                rackSet.erase(removedCd);
            }

            rack.push(demands[i]);
            rackSet.insert(demands[i]);
        }
    }

    cout << misses << endl;

    return 0;
}