#include <iostream>
#include <deque>
#include <fstream>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.in");
const int MAX = 5e6+1;
deque <int> q;
int n,k,v[MAX];
long long ans;

int main()
{
    in>>n>>k;
    for(int i=1;i<=n;i++)
        cin>>v[i];
    for(int i=1;i<=n;i++)
    {
        while(!q.empty()&&v[q.back()]>=v[i])
            q.pop_back();
        q.push_back(i);
        if(q.front()==i-k)
            q.pop_front();
        if(i>=k)
            ans=ans+v[q.front()];
    }
    out<<ans;
    return 0;
}