program pr1;
var f1, f2: text;
    a,b:integer;
begin
assign(f1,'input.dat');
assign(f2,'output.sol');
reset(f1);
readln(f1,a);
readln(f1,b);
rewrite(f2);
writeln(f2,b/2:10:2);
close(f1);
close(f2);
end.