#include <bits/stdc++.h>

using namespace std;

const int NMAX=(5*(1e6));

int N, K, i;

int A[NMAX+5];

deque <int> D;

long long ans;

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

    scanf("%d%d", &N, &K);

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

    D.push_back(1);

    for(i=2; i<=N; i++)
    {
        //Analiza amortizata:
        while(!D.empty() && A[D.back()] > A[i])
            D.pop_back();

        D.push_back(i);

        if(D.back() - D.front() >= K)
            D.pop_front();

        if(i>=K)
            ans+=A[D.front()];
    }

    printf("%d\n", ans);

    return 0;
}