#include <iostream>
#include <fstream>

#define maxn 5000010


int arr[maxn], deq[maxn];
int n,k;
long long s;
int fr=1, bk=0;

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int main()
{
    fin>>n;
    fin>>k;

    for(int i=1; i<=n; i++){
            fin>>arr[i];
    }

    for(int i=1; i<=n; i++){

        while(fr<=bk && arr[i]<=arr[deq[bk]])
            bk--;
        deq[++bk]=i;

        if(deq[fr]==i-k)
            fr++;

        if(i>=k)
            s+=arr[deq[fr]];

    }

    fout<<s;

    return 0;
}