#include <bits/stdc++.h>
using namespace std;

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

const int dim=5000009;

int n,k,v[dim];
int long long ans;

deque<int>dq;

signed main(){
        fin>>n>>k;
    for(int i=1;i<=n;i++){
        fin>>v[i];
    }
    for(int i=1;i<=n;i++){
        while(!dq.empty() && v[i]<=v[dq.back()]){
            dq.pop_back();
        }
        dq.push_back(i);
        while(!dq.empty() && i-dq.front()>=k){
            dq.pop_front();
        }
        if(i>=k){
            ans+=v[dq.front()];
        }
    }
        fout<<ans;
}