program ex;
type
 ss=array[1..50000,1..2]of longint;
 sz=array[0..1]of longint;
var
 f:ss;
 g,h:sz;
 n:longint;
procedure init;
 var
  i:longint;
 begin
  assign(input,'balance.in');
  assign(output,'balance.out');
  reset(input);
  rewrite(output);
  readln(n);
  for i:=1 to n do
   begin
    readln(f[i,1],f[i,2]);
    inc(g[f[i,1]]);
   end;
  close(input);
 end;
procedure qsort(l,r:longint);
 var
  i,j,x,y:longint;
 begin
  i:=l;j:=r;x:=f[(l+r)div 2,2];
  repeat
   while f[i,2]<x do inc(i);
   while x<f[j,2] do dec(j);
   if i<=j then
    begin
     y:=f[i,2];f[i,2]:=f[j,2];f[j,2]:=y;
     y:=f[i,1];f[i,1]:=f[j,1];f[j,1]:=y;
     inc(i);dec(j);
    end;
 until i>j;
 if l<j then qsort(l,j);
 if i<r then qsort(i,r);
 end;
procedure main;
 var
  i,j:longint;
  min,max:longint;
  flag:boolean;
 begin
  if g[0]>g[1] then min:=g[1] else min:=g[0];
  i:=1;j:=1;max:=0;
  h[f[1,1]]:=1;
  while i<n do
   begin
    if (h[1]=h[0]) then
     begin
      if f[j,2]-f[i,2]>max then max:=f[j,2]-f[i,2];
      inc(i);
      dec(h[f[i-1,1]]);
     end
     else begin
           if j<n then
            begin
             inc(j);inc(h[f[j,1]]);
             if h[f[j,1]]>min then
              begin
               inc(i);
               dec(h[f[i-1,1]]);
              end;
            end
            else begin
                  inc(i);
                  dec(h[f[i-1,1]]);
                 end;
          end;
   end;
  writeln(max);
  close(output);
 end;
begin
 init;
 qsort(1,n);
 main;
end.