#include <iostream>
#include <math.h>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <iomanip>
#include <stdlib.h>
#include <fstream>
#include <algorithm>
#include <string>
#include <set>
using namespace std;
int v[5000010];
ifstream f("deque.in");
ofstream g("deque.out");
int main()
{
    deque<int> Q;
    int suma =0 ;
    int n;
    int k;
    f>>n>>k;
    for(int i=1;i<=n;i++)
    {
        f>>v[i];
    }
    for(int i=1;i<=n;i++)
    {
        while(!Q.empty() && v[i] <= v[Q.back()])Q.pop_back();
        Q.push_back(i);
        
        if(Q.front() == i-k)Q.pop_front();
        if(i >=k )suma+=v[Q.front()];
    }
    g<<suma;
}