Do you have spent some time to think and try to solve those unsolved problem after one ACM contest?No? Oh, you must do this when you want to become a "Big Cattle".Now you will find that this problem is so familiar:The greatest common divisor GCD (a, b) of two positive integers a and b, sometimes written (a, b), is the largest divisor common to a and b. For example, (1, 2) =1, (12, 18) =6. (a, b) can be easily found by the Euclidean algorithm. Now I am considering a little more difficult problem:Given an integer N, please count the number of the integers M (0<M<N) which satisfies (N,M)>1.This is a simple version of problem “GCD” which you have done in a contest recently,so I name this problem “GCD Again”.If you cannot solve it still,please take a good think about your method of study.Good Luck!
，可以以心感悟，以此沉淀，足矣;耳听佳音，目极美好，
