#include <bits/stdc++.h>

using namespace std;
deque <int> q;
const int nmax=1e6*5+5;
int n,k,x,v[nmax];
long long s;
int main() {
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d %d", &n, &k);

    for (int i = 1; i <= n; ++i)
        scanf("%d ", &v[i]);
    for (int i = 1 ; i <= n; ++i) {

        while (!q.empty() && v[i]<=v[q.back()])
            q.pop_back();
        q.push_back(i);

        if (q.front() == i - k) q.pop_front();
        if (i>=k) s+=1LL* v[q.front()];

    }
    printf("%lld", s);
    return 0;
}