#include <iostream>
#include <fstream>
#include <deque>
#include <queue>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int a[5000001];
int main()
{   int i,j,n,k;
    long long s=0;
    fin>>n>>k;
    for(i=1;i<=n;++i)fin>>a[i];
    deque <int> d;
    for(i=1;i<=n;i++)
        {while(!d.empty()&&a[d.back()]>=a[i])
                d.pop_back();
         d.push_back(i);
         if(i-k==d.front())
            d.pop_front();
         if(i>=k)
             s+=a[d.front()];
        }
    fout<<s;
    return 0;
}