The Diversity of the Library of Alexandria

#include <bits/stdc++.h>
using namespace std;

#define fastio ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define Max(a, b) (a > b ? a : b)
#define Min(a, b) (a < b ? a : b)
#define SZ(a) (int)a.size()

inline void add(int x, unordered_map<int, int> &cnt) {
    cnt[ x ]++;
}

inline void rem(int x, unordered_map<int, int> &cnt) {
    cnt[ x ]--;
    if(cnt[ x ] == 0) cnt.erase(x);
}

inline int count(int x, unordered_map<int, int> &cnt) {
    add(x, cnt);
    int r = SZ(cnt);
    rem(x, cnt);
    return r;
}

void solve(){
    int n, k;
    cin >> n >> k;
    vector<int> arr(n);

    unordered_map<int, int> cnt, cnt_w;

    for(int &w : arr) cin >> w;
    long long ans = 0;
    int w = 0;

    for(int i = 0, j = 0; i < n; ++i) {

        w = Max(w, i);
        while(j < n and count(arr[j], cnt) <= k) {
            if(SZ(cnt_w) != k) {
                add(arr[j], cnt_w);
                w = j;
            }
            add(arr[j], cnt), ++j;
        }
        if(SZ(cnt_w) == k) ans += (j - w);

        rem(arr[i], cnt);
        rem(arr[i], cnt_w);

        while(w < j and SZ(cnt_w) != k) {
            ++w;
            add(arr[w], cnt_w);
        }
    }

    cout << ans << '\n';
}

int32_t main() {

    fastio;
    solve();

    return 0;
}