program banlance;
var
  a:array[0..50001,1..2]of longint;
  i,j,n,k,a1,m,a0,max:longint;

procedure sort(l,r:longint);
var
  i,j,x,y,z:longint;
begin
  i:=l; j:=r;
  x:=a[(l+r)div 2,1];
  repeat
    while a[i,1]<x do inc(i);
    while a[j,1]>x do dec(j);
    if not(i>j) then begin
      y:=a[i,1]; z:=a[i,2];
      a[i,1]:=a[j,1]; a[i,2]:=a[j,2];
      a[j,1]:=y; a[j,2]:=z;
      inc(i); dec(j);
    end;
    until i>j;
    if l<j then sort(l,j);
    if i<r then sort(i,r);
  end;

begin
  assign(input,'balance.in');
  assign(output,'balance.out');
  reset(input); rewrite(output);
  readln(n);
  fillchar(a,sizeof(a),0);
  for i:=1 to n do begin
    readln(k,m);
    a[i,2]:=k; a[i,1]:=m;
  end;
  sort(1,n); max:=0;
  for i:=1 to n do begin
    k:=0;
    for j:=i to n do begin
      if a[j,2]>0 then inc(k) else dec(k);
      if (k=0)and(max<a[j,1]-a[i,1]) then max:=a[j,1]-a[i,1];
    end;
  end;
  writeln(max);
  close(input); close(output);
end.