var sum,x:double;
    n,i,s,e,cnt:longint;
begin
readln(s,e,n);
for i:=1 to n do begin
 read(x);
 if (x>=s)and(x<=e) then sum:=sum+x
 else inc(cnt);
end;
 if cnt/n>0.1 then writeln('0.0')
 else writeln(sum/(n-cnt):0:4);
close(input);close(output);
end.