AC

#include <iostream>
#include <vector>
#include <queue>
#include <unordered_set>

using namespace std;

int main() {
    int M, N;
    cin >> M >> N;
    
    vector<int> words(N);
    for (int i = 0; i < N; ++i) {
        cin >> words[i];
    }
    
    queue<int> memoryQueue;
    unordered_set<int> memorySet;
    int dictionaryLookups = 0;
    
    for (const int& word : words) {
        if (memorySet.find(word) == memorySet.end()) {
            // Word not in memory, need to look up in dictionary
            dictionaryLookups++;
            
            if (memoryQueue.size() == M) {
                // Memory is full, remove the oldest word
                int oldestWord = memoryQueue.front();
                memoryQueue.pop();
                memorySet.erase(oldestWord);
            }
            
            // Add new word to memory
            memoryQueue.push(word);
            memorySet.insert(word);
        }
    }
    
    cout << dictionaryLookups << endl;
    
    return 0;
}