#include<fstream>
#include<deque>
using namespace std;

int a[5000010];
int n, k;
deque<int> Q;
long long s;

void solve();

int main()
{
	solve();
	return 0;
}

void solve()
{
	ifstream fin("deque.in");
	ofstream fout("deque.out");
	
	fin >> n >> k;
	
	for(int i = 1; i <= n; ++i)
	{
		fin >> a[i];
		
		while( !Q.empty() && a[i] <= a[Q.back() ] )
			Q.pop_back();
		
		Q.push_back(i);
		
		if( i - k == Q.front() )
			Q.pop_front();
		
		if( i >= k )
			s = s + a[ Q.front() ];
		
	}
	
	fout << s;
}