#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int> B;
int n,k,a[5000001];
long long s;
int main()
{   f>>n>>k;
    for(int i=1;i<=n;i++)
    {   f>>a[i];
        while(!B.empty() and a[B.front()]>a[i])
            B.pop_front();
        B.push_front(i);
        if(!B.empty() and i-B.back()>=k)
            B.pop_back();
        if(i>=k)   s+=a[B.back()];
    }
    g<<s;
    return 0;
}