uses
crt;
var
a:array[1..4,1..4]of integer;
i,j,sum:integer;
begin
clrscr;
sum:=0;
for i:=1 to 4 do
begin
for j:=1 to 4 do
begin
a[i,j]:=random(20);
write(a[i,j]:3,' ');
if i=j then
inc(sum,a[i,i])
end;
writeln
end;
writeln('sredn.arifm.=',sum/4:2:2);
readkey
end.