Friend HDU-1719 Friend number are defined recursively as follows.
(1) numbers 1 and 2 are friend number;
(2) if a and b are friend numbers, so is ab+a +b;
(3) only the numbers defined in (1
Friend HDU-1719 Friend number are defined recursively as follows.
(1) numbers 1 and 2 are friend number;
(2) if a and b are friend numbers, so is ab+a +b;
(3) only the numbers defined in (1