#include <iostream>
#include <cstdio>
#include <deque>

using namespace std;

const int NMax = 5000005;
int N, K;
long long sum;
deque < int > dq;
int v[NMax];
/*
push_front
pop_front
push_back
pop_back
*/

void Read()
{
    scanf("%d %d", &N, &K);

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

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    Read();

    dq.push_back(1);

    for(int i=2; i<=N; ++i)
    {
        if(dq.front() == i-K)
            dq.pop_front();

        while(!dq.empty() && v[dq.back()] > v[i])
        {
            dq.pop_back();
        }

        dq.push_back(i);

        if(i>=K)
        {
            sum += 1LL * v[dq.front()];
        }
    }

    cout << sum;

    return 0;
}