#include<iostream>
#include<fstream>
#include<set>
#include<deque>
using namespace std;
int main()
{ifstream f("deque.in");
ofstream h("deque.out");
long long s=0,a,n,k,i;
multiset<long> v;
deque<long> p;
f>>n>>k;
for(i=1;i<=k;i++)
{f>>a;
p.push_back(a);
v.insert(a);}
s=*v.begin();
for(i=k+1;i<=n;i++)
{	f>>a;
v.erase(p[0]);
v.insert(a);
p.pop_front();
p.push_back(a);
s=s+*v.begin();}

h<<s;
	
	
	
	
	return 0;}