#include <fstream>
#include <deque>
#define int long long
using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

int v[5000005];
int mn[5000005];

deque <int> dq;

signed main()
{
    int n, k;
    cin>>n>>k;
    for(int i=1; i<=n; i++)
    {
        cin>>v[i];
        if(i<=k)
        {
            while(!dq.empty() && v[dq.back()]>v[i])
            {
                dq.pop_back();
            }
            dq.push_back(i);
        }
    }
    mn[k]=v[dq.front()];
    for(int i=k+1; i<=n; i++)
    {
        while(dq.front()<=i-k)
        {
            dq.pop_front();
        }
        while(!dq.empty() && v[dq.back()]>v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        mn[i]=mn[i-1]+v[dq.front()];
    }
    cout<<mn[n];


    return 0;
}