http://acm.hdu.edu.cn/showproblem.php?pid=4001 Problem Description Do you remember our children time? When we are children, we are interesting in almost everything around ourselves. A little thing or

http://acm.hdu.edu.cn/showproblem.php?pid=4002Problem DescriptionEuler's Totient function, φ (n) [sometimes called the phi function], is used to determine the number of numbers less than n which