Link to this code:
https://cses.fi/paste/2ae8b02143146569c7990f//* 777 */
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define FAST_IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
void solve() {
int n, k; cin >> n >> k;
vector<int> vec(n);
for (auto &x : vec) cin >> x;
map<int,int> mp;
int cnt = 0;
for (int l = 0, r = 0 ; r < n ; ++r) {
mp[vec[r]]++;
while ((int) mp.size() > k) {
if(--mp[vec[l]] == 0) mp.erase(vec[l]);
++l;
}
cnt += r - l + 1;
}
cout << cnt;
}
int32_t main() {
FAST_IO
solve();
}