#include <iostream>
#include <fstream>
const int MAXN=5e6 + 1;

using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");

int v[MAXN];
int deq[MAXN];
int main()
{
    int n,k;
    in>>n>>k;
    for(int i=1;i<=n;i++)
        in>>v[i];
    int fr = 1, bk = 0;
    long long s=0;
    for(int i=1;i<=n;i++)
    {
        while(v[deq[bk]]>=v[i] && fr<=bk)
            bk--;
        bk++;
        deq[bk]=i;
        if(i-deq[fr] >= k)
            fr++;
        if(i>=k)
            s=s+v[deq[fr]];
        //cerr << i << " " << v[deq[fr]] << "\n" ;

    }
    out<<s;
    return 0;
}