using namespace std;
#include<fstream>
#include<deque>
#include<algorithm>
#define MIN 10000001
#define inFile "deque.in"
#define outFile "deque.out"
int main ()
{
	deque<int> v;
	int n,k,x,min=MIN,s=0;
	bool ok;
	ifstream f(inFile);
	f>>n>>k;
	for(int i=1;i<=k;i++)
	{
		f>>x;
		if(x<min)
			min=x;
		v.push_back(x);
	}
	s+=min;
	fstream g(outFile);
	while(k!=n)
	{
		if(!(min^(*v.begin())))
			ok=true;
		v.pop_front();
		f>>x;
		v.push_back(x);
		if(ok)
			min=*min_element(v.begin(),v.end());
		else
			if(x<min)
				min=x;
		k++,s+=min;
	}
	
	f.close();
	
	g<<s;
	g.close();
	
	return 0;
}