var a,b,c,v:array[0..100000]of longint;
    n,i,j,k,o:longint;
    f:text;
begin
   assign(f,'heavymetal.in');
   reset(f);
   read(f,n);
   for i:=1 to n do
   read(f,a[i],b[i]);
   close(f);
   for i:=1 to n do
   begin
   k:=i;
   while b[k]<b[k div 2] do
   begin
   o:=a[k];
   a[k]:=a[k div 2];
   a[k div 2]:=o;
   o:=b[k];
   b[k]:=b[k div 2];
   b[k div 2]:=o;
   k:=k div 2;
   end;
   end;
   for i:=1 to n do
   begin
   c[i]:=i;
   while(a[i]<b[c[i]])do
   c[i]:=c[i]-1;
   end;
   for i:=1 to n do
   begin
   v[i]:=v[c[i]]+b[i]-a[i];
   if v[i]<v[i-1] then v[i]:=v[i-1];
   end;
   assign(f,'heavymetal.out');
   rewrite(f);
   writeln(f,v[n]);
   close(f);
end.