#include <iostream>
#include <queue>
#include <algorithm>
#include <set>
#include <map>
#include <stack>
#include <vector>
#include <string>
#include <deque>
#include <unordered_map>
#include <unordered_set>
#include <cmath>
#include <iomanip>

using namespace std;

#define ll long long

int n, k;
vector<int> values;

void ReadData() {
    cin >> n >> k;

    int value = 0;
    for(int i = 0; i < n; i++){
        cin >> value;
        values.push_back(value);
    }
}

void Solve() {
    deque<int> dq;
    long long result = 0;

    for (int i = 0; i < n; i++){
        while (!dq.empty() && dq.front() <= i - k) dq.pop_front();
        while (!dq.empty() && values[dq.back()] > values[i]) dq.pop_back();
        dq.push_back(i);
        if (i >= k - 1) result+= values[dq.front()];    
    }
    cout << result << "\n";
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    int t = 1;
    // cin >> t; // Uncomment for multiple test cases
    while (t--) {
        ReadData();
        Solve();   
    }
    return 0;
}