LAZY PASCAL

program sss;
var i,s,n,nmax,maxx,k:longint;
    a:array[0..1000000]of longint;

procedure nhap;
var i,x,c:longint;
begin
    readln(n,k);
    nmax:=0;
    for i:=1 to n do
       begin
        readln(c,x);
            a[x]:=c;
        if nmax<x then nmax:=x;
    end;
end;

procedure giai;
var i:longint;
begin
    maxx:=-1;
    s:=0;
    for i:=0 to (2*k) do s:=s+a[i];
    if s>maxx then maxx:=s;
    for i:=2*k+1 to nmaxx do
    begin
        s:=s+a[i]-a[i-(2*k+1)];
        if s>maxx then maxx:=s;
    end;
    writeln(maxx);
end;

begin
    assign(input,'lazy.inp');reset(input);
    assign(output,'lazy.out');rewrite(output);
    nhap;
    giai;
end.