#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() {
    multiset<int> pq;
    int result = 0;
    for (int i = 0; i < k; i++){
        pq.insert(values[i]);
    }
    result+= *pq.begin();

    for (int i = k; i < n; i++){
        auto it = pq.find(values[i - k]);
        pq.erase(it);
        pq.insert(values[i]);
        result+= *pq.begin();
    }

    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;
}