program sdss;
uses crt;
var a,b,i:integer;
c:real;
begin
clrscr;
readln(a,b);
for i:=a to b do
c:c+i;
c:=c/(b-a+1);
writeln(c:2:4);
readkey;
end.
program sdss;
uses crt;
var a,b,i:integer;
c:real;
begin
clrscr;
readln(a,b);
for i:=a to b do
c:c+i;
c:=c/(b-a+1);
writeln(c:2:4);
readkey;
end.