#include <iostream>
#include <fstream>
#include <deque>
#include <queue>
#define N 5000005
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> D;
queue <int> C;
int n,k;
int v[N];
void Citire()
{
    int i;
    for(i=1;i<=n;i++)
        fin>>v[i];
}

int main()
{   int i,s=0;
    fin>>n>>k;
    Citire();
    for(i=1;i<=n;i++)
    {
        while(!D.empty()&&v[D.back()]>=v[i])
            D.pop_back();
        D.push_back(i);
        if(i-k==D.front())
            D.pop_front();
        if(i>=k)
            s+=v[D.front()];
    }
    fout<<s;
    return 0;
}