#include <bits/stdc++.h>
#define L long long
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
L v[5000001],s;
multiset<L>a;
int n,k;
int main()
{
    in>>n>>k;
    for(int i=1; i<=n; ++i)
    {
        in>>v[i],a.insert(v[i]);
        if(i==k)
            s+=(*a.begin());
        else if(i>k)
            a.erase(a.find(v[i-k])),s+=(*a.begin());
    }
    out<<s;
}