#include <bits/stdc++.h>
using namespace std;
int n,k,i,a[100002],s;
deque<int> m;
int main()
{ cin >> n >> k;
for(i = 1; i <= n; i++)cin>>a[i];
m.push_back(1);
for(i = 2; i <= n; i++)
{while(!m.empty() && a[i]<=a[m.back])m.pop_back();
m.push_back(i);
}
s=a[m.front()];
for(i=k+1;i<=n;i++)
{while(!m.empty() && m.front()<=i)m.pop_front();
while(!m.empty() && a[i]<=a[m.back])m.pop_back();
m.push_back(i);
s+=a[m.front()]
}
cout<<s;
return 0;
}