#include <fstream>
#include <queue>
#include <deque>
#define N 5000005

using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");

int n, v[N];
deque <int> D;
int main()
{
    int i,k;
    long long s=0;
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>v[i];
    for(i=1;i<=n;i++)
    {
        while(!D.empty() && v[D.back()]>=v[i])
            D.pop_back();
        D.push_back(i);
        if(i-k==D.front())
            D.pop_front();
        if(i>=k)
            s+=v[D.front()];
    }
    g<<s;
    return 0;
}