#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;
priority_queue<int> q;
ifstream cin("bleach.in");
ofstream cout("bleach.out");
long long rez,s;
int n, k,i,x,aux;
int main(){
	cin >> n >> k;
	for(i = 1;i<=k+1;i++){
		cin>>x;
		q.push(-x);
	}
	i = k +1;
	while(!q.empty()){
		i++;
		aux = -q.top();
	//	cout<<s<<" " << aux <<" "<<q.top()<<"\n";
		q.pop();
		if(aux-s>rez)rez = aux -s;
		s= s + aux;
		if(i <= n){
			cin >>x;
			q.push(-x);
		}
	}
	cout <<1LL*rez; 
}