#define NMAX 5000005
#include <iostream>
#include <deque>
using namespace std;

deque <int>D;
long long a[NMAX];
int n, k, x;
long long sum=0;


int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d %d", &n, &k);
    for(int i=1; i<=n; i++)
    {
        scanf("%lld", &a[i]);
        while(!D.empty() && a[D.back()] >= a[i])
            D.pop_back();
        D.push_back(i);

        while(D.front() <= i-k)
            D.pop_front();

        if(i >= k)
            sum += a[D.front()];
    }
    printf("%lld", sum);
    return 0;
}