#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
const int nMax = 5000005;
int a[nMax];
deque <int> dq;
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(!dq.empty() && a[dq.back()] >= a[i]) {
            dq.pop_back();
        }
        dq.push_back(i);
        while(i - k >= dq.front()) {
            dq.pop_front();
        }
        if(i >= k) {
            ans += a[dq.front()];
        }
    }
    g << ans << "\n";
    return 0;
}