program aaa;

{$APPTYPE CONSOLE}

var t:array [1..5] of integer;
s:real;
i:integer;
begin
for i:=1 to 5 do read(t[1]);
s:=0;
for i:=1 to 5 do s:=s+t[1];
writeln(s/10);
readln;
readln;
end.