#include <fstream>
#include <deque>
#include <vector>
using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");
deque <int> d;
int A[5000001];
int n,k;
long long Min=10000001,sum,x;
int main()
{
    cin>>n>>k;
    for(int i=1; i<=n; ++i)
        cin>>A[i];
    for(int i=1; i<=n; ++i)
    {
        while(!d.empty() && A[i] <= A[d.back()]) d.pop_back();
        d.push_back(i);
        if(d.front() == i-k) d.pop_front();
        if(i>=k) sum += A[d.front()];
    }
    cout<<sum;
    return 0;
}