#include <bits/stdc++.h>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
const int nMax = 5000003;
long long 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(D.front() <= i - k) {
            D.pop_front();
        }
        if(i >= k) {
            ans += a[D.front()];
        }
    }
    g << ans <<"\n";
    return 0;
}