import java.util.*;publicclassMain{static Scanner sc =newScanner(System.in);publicstaticvoidmain(String[] args){int n = sc.nextInt();//n个数int m = sc.nextInt();//求m个连续的数的最大和int number[]=newint[n];for(int i =0; i < n; i++){
number[i]= sc.nextInt();}
List<Integer> list =newArrayList<>();int numb []=newint[number.length+m];//形成一个环//拷贝数组
System.arraycopy(number,0, numb,0, number.length);for(int i =0; i < m; i++){
numb[(number.length+i)]= number[i];}for(int i =0; i < numb.length; i++){if((i+m)<=numb.length){int num =0;for(int j = i; j < m+i; j++){
num = num + numb[j];}
list.add(num);}}
Object[] objects = list.toArray();
Arrays.sort(objects);
System.out.print((int)objects[objects.length-1]);}}