#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int a[5000001],n ,k;

int main()

{ deque<int> d;
int i;
long long s=0;
fin>>n>>k;
for(i=1;i<=n;i++)
        fin>>a[i];
for(i=1;i<=n;i++)
{ while(!d.empty() && a[d.back()]>=a[i])
    d.pop_back();
d.push_back(i);
while(i-k==d.front())
    d.pop_front();
if(i>=k) s+=a[d.front()];
}
fout<<s;

    return 0;
}