program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

    var
    s : array [0..105, 0..105] of integer;
    i, j, max, max1 : integer;
    x, n : shortint;
    q : boolean;

begin
   max := -100;
   max1 := -100;
   q := false;
   read(n);
   for i := 0 to n do
     begin
       s[0, i] := 0;
       s[i, 0] := 0;
     end;
   for i := 1 to n do
   for j := 1 to n do
     begin
       read(x);
       if x >= 0 then q := true;
       if max1 < x then max1 := x;
       s[i, j] := s[i-1,j] + s[i,j-1] + x - s[i-1,j-1];
       if s[i, j] > max then max := s[i, j];
       if s[i, j] < 0 then s[i, j] := 0;
     end;
   if q then  writeLn(max)
   else writeLn(max1);
end.