#include <bits/stdc++.h>

using namespace std;
ifstream f("deque.in");
ofstream g"deque.out");

const int maxx.dim=5000005;
int v[maxx.dim];

int main()
{
    int n, k;
    long long sum=0;
    deque<int>mini, minipos;
    f>>n>>k;
    for(int i=1; i<=n; i++)
    {
        f>>v[i];
    }
    for(int i=1; i<=n+1; i++)
    {
        while(!mini.empty() and mini.back()>v[i])
        {
            mini.pop_back();
            minipos.pop_back();

        }
        if(i>k)
        {
            sum=sum+mini.front();
        }

        if(!mini.empty() and i-k>=minipos.front())
        {
            minipos.pop_front();
            mini.pop_front();
        }
        mini.push_back(v[i]);
        minipos.push_back(i);
    }
    g<<sum;
    return 0;
}