PROGRAM XoanOc;
USES Crt;
VAR a:ARRAY[1..20,1..20]OF BYTE;
i,j,k,x,l,n,ghi:INTEGER;
BEGIN     
Write('Nhap so N = ');            
Readln(x);
n:=x; 
k:=1 ;l:=1;  ghi :=1;     
REPEAT                                        
BEGIN
BEGIN  
 i:= k;
FOR j:=l TO n DO
BEGIN    
a[j,i]:= ghi ;
inc(ghi);
END;
k:= k+1;    
FOR i:= k TO n DO            
BEGIN
a[j,i]:= ghi ; 
inc(ghi);
END;                          
n:= n-1;
FOR j:=n DOWNTO l DO 
BEGIN 
a[j,i]:=ghi; 
inc(ghi);
END;              
FOR i:= n DOWNTO k DO
BEGIN
a[j,i
]:=ghi;
inc(ghi);
END;      
l:= l+1;
END ;                              
END;
UNTIL n=0 ; 
Writeln;
Writeln('Day so da duoc sap xep : ');
Writeln;
FOR i:= 1 TO x DO
BEGIN
FOR j:= 1 TO x DO
Write(a[i,j]:4); 
Writeln;
END;
Readln;
END.