#include <cstdio>
#include <queue>

using namespace std;

deque<int> q;
int v[5000010];

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    int n,k;
    long long sol=0;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++) scanf("%d",&v[i]);
    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) sol+=v[q.front()];
    }
    printf("%lld",sol);
    return 0;
}