DAYCON1034 Pascal

var a:array[0..100000]of int64;
    s:array[0..100000]of int64;
    d,maxx:int64;
    n,k,i,j:longint;
procedure nhap;
var i:longint;
begin
    readln(n,k);
    for i:=1 to n do read(a[i]);        
end;

procedure giai;
var i:longint;
begin
    //tinh s1
    for i:=1 to k do s[1]:=s[1]+a[i];
    //tinh s2 den s[n-k+1]
    for i:=2 to n-k+1 do 
        s[i]:=s[i-1]-a[i-1]+a[i+k-1];
    //tim maxx
    maxx:=s[1];
    for i:=2 to n-k+1 do
        if s[i]>maxx then maxx:=s[i];
      write(maxx);
end;
begin
    assign(input,'DAYCON1034.inp');reset(input);
    assign(output,'DAYCON1034.out');rewrite(output);
    nhap;
    giai;
end.