#include <cstdio>
#include <queue>
using namespace std;
const int NMAX = 5000000;
int v[NMAX + 5];
typedef pair<int,int>ii;
deque <ii>q;
int main()
{
    freopen("deque.in" , "r" , stdin);
    freopen("deque.out" , "w" , stdout);
    int n , i , k;
    long long s = 0;
    scanf("%d%d" , &n , &k);
    for(i = 1 ; i <= n ; i ++)
      scanf("%d" , &v[i]);
    for(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 = s + q.front().first;
        }
    }
    printf("%d" , s);
    return 0;
}