#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

int n,k,x,cnt,v[5000002];
long long suma;
deque <int> q;
int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++)cin>>v[i];
    for(int i=1;i<=n;i++)
    {
        x=v[i];
        while(q.size() && q.front()>x)
            q.pop_front();

        q.push_front(x);


        if(i>=k)
        {
            if(v[i-k]==q.back()) q.pop_back();
            suma+=q.back();
            ///cout<<q.back()<<' ';
        }
    }
    cout<<suma;
    return 0;
}