uses crt;
var A : array[1..100] of integer; i, N : integer;
begin
clrscr; randomize;
write('Nhap so phan tu : '); readln(N);
for i := 1 to N do
begin
A[i] := random(20) - random(20);
writeln('Phan tu thu ', i ,' : ', A[i]);
end;
write('Phan tu vi tri chan : ');
for i := 1 to N do
if i mod 2 = 0 then write(a[i],' ');
readln
end.