program book;
var n,i:integer;
  f,min,max:longword;
  w,v:array[0..402]of word;
procedure heap(var n:integer);
var p:word;
begin
  min:=max;
  for i:=1 to n-1 do
    if w[i]-v[i]+w[i+1]-v[i+1]<min then
    begin
      min:=w[i]-v[i]+w[i+1]-v[i+1];
      p:=i;
    end;
  w[p+1]:=w[p]+w[p+1];
  v[p+1]:=v[p]+v[p+1];
  f:=f+min;
  n:=n-1;
  for i:=p to n do
  begin
    w[i]:=w[i+1];
    v[i]:=v[i+1];
  end;
  if n>2 then heap(n) else if n=2 then f:=f+w[1]-v[1]+w[2]-v[2];
end;
begin
  assign(input,'book.in'); reset(input);
  assign(output,'book.out'); rewrite(output);
  readln(n);
  max:=0; f:=0;
  for i:=1 to n do begin readln(w[i],v[i]); max:=max+w[i]-v[i]; end;
  heap(n);
  writeln(f);
  close(input); close(output);
end.