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.