#include <bits/stdc++.h>
#define ll long long
using namespace std;
 
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> minimum;
ll result;
int v[5000010];
 
int main() {
    int n, k;
 
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
        fin >> v[i];
 
    for (int i = 1; i <= n; i++) {
        while (!minimum.empty() && v[i] <= v[minimum.back()])
            minimum.pop_back();
        minimum.push_back(i);
 
        if (i - k  == minimum.front())
            minimum.pop_front();
 
        if (i >= k)
            result += v[minimum.front()];
    }
 
    fout << result;
 
    return 0;
}