#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");


int main()
{
    int n,k;
    fin >> n >> k;
    deque <int> dq;
    vector<int>a(n+1);
    for (int i=1;i<=n;i++){
        fin >> a[i];
    }
    ll sum=0;
    for (int i=1;i<=n;i++){
        while (!dq.empty() && a[dq.back()]>=a[i])
            dq.pop_back();
        dq.push_back(i);
        if (dq.front()<=i-k)
            dq.pop_front();
        if (i>=k)
            sum+=a[dq.front()];
    }
    fout << sum;
    return 0;
}