#include<bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int N,K,v[5000001],s;
deque <int> deq;
int main()
{
    f>>N>>K>>v[1];
    deq.push_back(1);
    for(int i=2;i<=N;++i){
        f>>v[i];
        while(!deq.empty()&&v[i]<=v[deq.back()])deq.pop_back();
        deq.push_back(i);
        if(i-K==deq.front())deq.pop_front();
        if(K<=i)s+=v[deq.front()];
    }
    g<<s;
    return 0;
}