///#include <iostream>
#include <fstream>
#include <deque>
#include <queue>
#define N 5000005
using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

int n,v[N];
deque<int> D;

int main()
{
    int i,k;
    long long s=0;
    cin>>n>>k;
    for(i=1; i<=n; ++i) cin>>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()];
        }
    cout<<s;
    return 0;
}