Verified answer

var a:array[1..100,1..100] of integer;

i,j,s,n,k:integer;

Begin

  read(n);

  for i:= 1 to n do

    for j:= 1 to n do begin

      read(a[i,j]);

      if i mod 2=0 then begin

         k:=k+1;

         s:=s+a[i,j];

      end;

    end;

    writeln(s/k);

end.