program summ;
var
a:array[1..100,1..100] of integer;
N,i,j,sa,sb,sc,s:integer;
 begin
  repeat
   writeln('vvedite N');
   readln(N);
  if (n<1) then 
   writeln('nedopustimoe znachenie');
  until (n>=1);
  for i:=1 to n do
   for j:=1 to n do
     begin
      writeln('vvedite a[',i,',',j,']');
      readln(a[i,j]);
     end;
     begin
     sa:=0;
      for i:=1 to n do
       for j:=1 to (round(N/2)-1) do
        sa:=sa+a[i,j];
     sb:=0;
      for i:=(round(n/2)+1) to n do
       for j:=(round(n/2)) to i do
        sb:=sb+a[i,j];
     sc:=0;
      for i:=1 to round(n/2) do
       for j:=round(n/2) to (n-i+1) do
        sc:=sc+a[i,j];
     end;
  s:=sb+sc+sa;
  writeln('s=',s);
 end.