#include <cstdio>
#include <deque>

using namespace std;

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);

    deque <int> q;
    int n, k, v[5000001];
    scanf("%d%d", &n, &k);
    for(int i=1; i<=n; i++) scanf("%d", &v[i]);

    long long sum=0;
    for(int i=1; i<=n; i++)
    {
        while(!q.empty() && v[i]<=v[q.back()]) q.pop_back();
        q.push_back(i);
        if(q.front() <= i-k) q.pop_front();
        if(i >= k) sum+=v[q.front()];
    }
    printf("%lld", sum);
}