uses crt;
var a:array[1..100]of integer;
n,dem,i,t:integer;
begin
clrscr;
write('Nhap n='); readln(n);
for i:=1 to n do
begin
write('A[',i,']='); readln(a[i]);
end;
dem:=0;
t:=0;
for i:=1 to n do
if i mod 2=1 then
begin
inc(dem);
t:=t+a[i];
end;
writeln('Trung binh cong cac phan tu o vi tri le la: ',t/dem:4:2);
readln;
end.