#include <bits/stdc++.h>

using namespace std;

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

deque <int> q;
int n,k,i,v[5000100];
long long s;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++)
    {
        f>>v[i];
        while(!q.empty() && v[i]<v[q.back()])q.pop_back();
        q.push_back(i);

        while(!q.empty() && q.front()<=i-k)q.pop_front();

        if(i>=k)s+=v[q.front()];
    }
    g<<s;
    return 0;
}