B'Dreamoon wants to climb up a stair of n steps. He can climb 1 or 2 steps at each move. Dreamoon wants the number of moves to be a multiple of an integer m. What is the minimal number of moves making him climb to the top of the stairs that satisfies his condition? The single line contains two space separated integers n, m (0 xe2 x80 x89< xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x8910000, xe2 x80 x891 xe2 x80 x89< xe2 x80 x89m xe2 x80 x89 xe2 x89 xa4 xe2 x80 x8910). Print a single integer -- the minimal number of moves being a multiple of m. If there is no way he can climb satisfying condition print xe2 x80 x89- xe2 x80 x891 instead. For the first sample, Dreamoon could climb in 6 moves with following sequence of steps: {2, 2, 2, 2, 1, 1}. For the second sample, there are only three valid sequence of steps {2, 1}, {1, 2}, {1, 1, 1} with 2, 2, and 3 steps respectively. All these numbers are not multiples of 5.'...