#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,u,p,i,v[5000005],d[5000005],s;
int main()
{
    fin>>n>>k;
    for(i=1;i<=n;i++) fin>>v[i];
    d[1]=1;
    u=p=1;
    for(i=2;i<=n;i++)
    {
        while(v[i]<=v[d[u]]&&p<=u) u--;
        u++;
        d[u]=i;
        if(i-d[p]==k) p++;
        if(i>=k) s+=v[d[p]];
    }
    fout<<s;
    return 0;
}