var
a,kol,sum,i:integer;
sr:real;
begin
kol:=0;
sum:=0;
for i:=1 to 12 do
begin
readln(a);
if not odd(a) then
begin
inc(kol);
sum:=sum+a;
end;
end;
sr:=sum/kol;
writeln(sr);
end.
var
a,kol,sum,i:integer;
sr:real;
begin
kol:=0;
sum:=0;
for i:=1 to 12 do
begin
readln(a);
if not odd(a) then
begin
inc(kol);
sum:=sum+a;
end;
end;
sr:=sum/kol;
writeln(sr);
end.