#include <iostream>
#include <bits/stdc++.h>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long n,k,i,Min1,Min2,s,x,y,a[5000010];
deque <long long> d;
int main()
{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;
}