var a,b,c,max : real;
begin
read(a,b,c);
max:=(a+b+abs(a-b))/2;
max:=(max+c+abs(max-c))/2;
writeln(max);
end.
var a,b,c,max : real;
begin
read(a,b,c);
max:=(a+b+abs(a-b))/2;
max:=(max+c+abs(max-c))/2;
writeln(max);
end.