program diagonale; uses math;
type vector1=array[0..2001] of int64;
     buf=array[0..1 shl 17] of char;
var dp,ds:vector1; max1,max2:int64;
    n,i,j,x:longint; ff1,ff2:buf;
    f1,f2:text;
begin
assign (f1,'diagonale.in');
assign (f2,'diagonale.out');
reset (f1);
rewrite (f2);
settextbuf(f1,ff1);
settextbuf(f2,ff2);
readln (f1,n);
for i:=1 to n do
for j:=1 to n do begin
read (f1,x);
dp[n+i-j]:=dp[n+i-j]+x;
ds[i+j-1]:=ds[i+j-1]+x;
end;
max1:=-1 shl 33; max2:=max1;
for i:=1 to 2*n-1 do begin
if dp[i]>max1 then max1:=dp[i];
if ds[i]>max2 then max2:=ds[i];
end;
writeln (f2,max(max1,max2));
close (f1);
close (f2);
end.