#include <bits/stdc++.h>

using namespace std;

int N, K, v[5000005];
deque<int> deq;

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]);

    long long sum = 0;
    for(int i = 1; i <= N; ++i) {
        while(!deq.empty() && v[deq.back()] > v[i])
            deq.pop_back();

        deq.push_back(i);

        while(!deq.empty() &&  i - deq.front() >= K)
            deq.pop_front();
        if(i >= K)
            sum += v[deq.front()];
    }
    printf("%lld\n", sum);

    return 0;
}