#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
deque <int> d;
ifstream in ("deque.in");
ofstream out ("deque.out");

long long n,k,i,j,l,m,s=0,v[5000001];
int main()
{
in>>n>>k;
for(i=1;i<=n;i++){in>>v[i];}
d.push_back(1);
for(i=2;i<=n;i++)
{while(!d.empty()&&v[d.back()]>v[i])
{if(d.size()!=0)
d.pop_back();
else break;


}


d.push_back(i);
if(d.back()-d.front()>=k){d.pop_front();}

if(i>=k){s=s+v[d.front()];}

}

out<<s;


    return 0;
}