#include<fstream>
#include<string>
#include<deque>
using namespace std;
#define goguta pair<int,int>
const int NMAX=5000000;
int v[NMAX+5];
deque<goguta> q;

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    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(goguta(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;
}