#include <iostream>
#include <fstream>


using namespace std;
const int N=5e6;

int dq[N+1], v[N+1];

int main()
{
ifstream cin("deque.in");
ofstream cout("deque.out");
int p=0,u=0;
    int k, i, n;
    long long ans=0;
    cin>>n>>k;
    for(i=1; i<=n; i++)
        cin>>v[i];
    for(i=1; i<=n; i++)
        {
        while(p && u && p<=u && i-dq[p]>=k)
            ++p;
        while(p && u && p<=u && v[dq[u]]>=v[i])
            --u;
        dq[++u]=i;
        if (p == 0)
            p = 1;
        if(i>=k) {
            ans += v[dq[p]];

            }

        }
        cout<<ans;
        return 0;
}