#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

int n, a[5000002];
deque<int>d;

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