#include<fstream>
#include<deque>
#define ii pair<int,int>
using namespace std;
int v[5000005];
int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    deque<ii> q;
    int n,k
    long long s=0;
    cin>>n>>k;
    for(int i=1;i<=n;++i)
        cin>>v[i];
    for(int i=1;i<=n;++i)
    {
        while(!q.empty() && q.back().first>=v[i])
            q.pop_back();
    q.push_back(ii(v[i],i));
    if(i>=k)
    {
        while(!q.empty() && i-q.front().second+1>k)
            q.pop_front();
        s+=q.front().first;
    }
    }
    cout<<s;
    return 0;
}