Program HOC24;
var i,n: integer;
t: longint;
begin
write('Nhap so phan tu: '); readln(n);
for i:=1 to n do
begin
write('Nhap so thu ',i,': '); readln(a[i]);
end;
t:=0;
for i:=1 to n do if i mod 2=0 then t:=t+a[i];
write('Tong cac so chan la: ',t);
readln
end.