#include <iostream>
#include <fstream>
#include <deque>
#include <queue>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque < int > d;

int n,k,x;
int v[5000001];
int main()
{
    int i,j;long long s=0;
    fin>>n>>k;
    for(i=1;i<=n;++i)fin>>v[i];
    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;
}