#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long int n,k,i,V[5000005],p,z;
deque<long long int>Q;
int main()
{
    f >>n >>k;
    for(i=1;i<=n;i++)f>>V[i];
    for(i=1;i<=n;i++)
    {
        p++;
        while(!Q.empty() && V[i]<=V[Q.back()])Q.pop_back();
        Q.push_back(i);
        while(!Q.empty() && i-Q.front()>=k)Q.pop_front();
        if(p>=k && !Q.empty())z+=V[Q.front()];

    }
   g<<z;
}