#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    ifstream f("deque.in");
    
    int n, k, l=0, r=0;
    int v[5000001];
    int v2[5000001];
    int sum=0;

    f>>n>>k;
    
    for (int i=1; i<=n; i++)
        f>>v[i];

    for (int i=1; i<=n; i++)
    {
        
        while (l<=r && v[v2[r]]>=v[i])
        {
            r--;
        }
        
        r++;
        v2[r] = i;
        
        if (v2[l]==i-k)
            l++;
            
        if (i >= k)
            sum +=v[v2[l]];
    }

    ofstream g("deque.out");
    
    g<<sum;
    f.close();
    g.close();
    return 0;
}