#include<bits/stdc++.h>
#define in f
#define out g
#define maxx 5000010
using namespace std;

ifstream f ("deque.in");
ofstream g ("deque.out");


int n;
int k;
long long s;
int v[maxx];
deque<int>d;

int main() {

    in >> n;
    in >> k;

    for(int i = 1; i <= n; i++) {
        in >> v[i];

        while(!d.empty() && v[i] <= v[d.back()]) {
            d.pop_back();
        }
        d.push_back(i);
        if(i - k == d.front()) {
            d.pop_front();
        }
        if(i >= k) {
            s = s + v[d.front()];
        }
    }
    out << s;

}