Introduction - If you have any usage issues, please Google them yourself
0-9 in the number 4 was selected to form the 4-digit, (which can repeat the number 10 may or may not be repeated, this time we only discuss the case of non-repetition, that is, 8854,4154 such value is not .1234,5678 of such a value is legal.) and then you guess the value of computer do you think the results are given with xAyB that, A said that you guess right, and also the location of the correct value of X months, B that you guess right, but the location of the numerical errors are Y months.