#include <bits/stdc++.h>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
deque <int> dq;
int n,k,a[5000002];
long long sum=0;
int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;++i)
        fin>>a[i];
    for(int i=1;i<=n;++i){
        while(!dq.empty() && a[dq.back()]>=a[i])dq.pop_back();
        dq.push_back(i);
        if(dq.front()==i-k)dq.pop_front();
        if(i>=k)sum+=a[dq.front()];
    }
    fout<<sum;
    return 0;
}