var a: array [1..20] of integer; 
i, x, y: integer; 
s: real; 
begin
for i:=1 to 20 do
readln (a[i]); 
x:=0; y:=0;
for i:=1 to 20 do
if a [i] > 0 then
begin
x:= x + 1;
y:= y + a[i];
end;
s:= y / x;
write(s);
end.