program book;
var
  f,g:array[1..400,1..400]of longint;
  i,j,k,n,min:longint;
  w,v:array[1..400]of longint;
begin
  assign (input,'book.in');
  reset (input);
  assign (output,'book.out');
  rewrite (output);
    readln (n);
    for i:=1 to n do
      readln (w[i],v[i]);
    for i:=1 to n do
      for j:=i to n do
        if i=j then
          g[i,j]:=w[i]-v[i]
        else
          g[i,j]:=g[i,j-1]+w[j]-v[j];
   for i:=n-1 downto 1 do
     for j:=i+1 to n do
     begin
       min:=maxlongint;
       for k:=i to j-1 do
         if f[i,k]+f[k+1,j]+g[i,j]<min then
           min:=f[i,k]+f[k+1,j]+g[i,j];
       f[i,j]:=min
     end;
   writeln (f[1,n]);
  close (input);
  close (output)
end.