#include <bits/stdc++.h>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
const int nMax = 5000005;
int a[nMax];
deque <int> d;
int main()
{
    int n, k;
    f >> n >> k;
    for(int i = 1; i <= n; i++) {
        f >> a[i];
    }
    long long ans = 0;
    for(int i = 1; i <= n; i++) {
        while(!d.empty() && a[d.back()] >= a[i]) {
            d.pop_back();
        }
        d.push_back(i);
        while(i - d.front() >= k) {
            d.pop_front();
        }
        if(i >= k) {
            ans += a[d.front()];
        }

    }
    g << ans << "\n";
    return 0;
}