var a:array[1..120] of longint;
b,i,k,j,n,m,x:longint;
begin
readln(n,m);
for i:=1 to m do read(a[i]);
for i:=m+1 to n do
begin
read(b);
k:=1;
for j:=2 to m do
if a[j]<a[k] then k:=j;
a[k]:=a[k]+b;
end;
x:=0;
for i:=1 to m do
if a[i]>x then x:=a[i];
writeln(x);
end.