#include <cstdio>
#include <bits/stdc++.h>
#include <deque>
using namespace std;

int n,k,i,a[5000005];
long long s;
deque <int> d;
int main()
{
    ifstream f("deque.in");
ofstream g("deque.out");

    f>>n>>k;
for (i=1;i<=n;i++)
{f>>a[i];
while (!d.empty() && a[d.back()]>=a[i])
d.pop_back();

d.push_back(i);
if (i-d.front()==k) d.pop_front();
    if(i>=k)s=s+a[d.front()];
    }

    g<<s;

     return 0;
}