#include <bits/stdc++.h>
#define ll long long

using namespace std;

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

ll n,k,s;
int v[5000200];
deque <int> dq;

int32_t main()
{
    f>>n>>k;
    for(int i=1; i<=n; i++)
    {
        f>>v[i];
        while(!dq.empty() and v[dq.back()]>=v[i])
            dq.pop_back();
        while(!dq.empty() and dq.front()<=i-k)
            dq.pop_front();
        dq.push_back(i);
        if(i>=k)
            s+=v[dq.front()];
    }
    g<<s;
    return 0;
}