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

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

const int nmax=5e6+4;
int n,k,v[nmax];
long long ans;

void read(){
in>>n>>k;
for(int i=1;i<=n;i++)
in>>v[i];
}

void solve(){
deque<int>dq;
for(int i=1;i<=n;i++)
{
 while(!dq.empty()&&v[i]<=v[dq.back()])
    dq.pop_back();

  dq.push_back(i);

 if(i-k==dq.front())
    dq.pop_front();

 if(i>=k) ans=ans+v[dq.front()];
}
out<<ans;
}


int main(){
read();
solve();

return 0;
}