B'Vasya will fancy any number as long as it is an integer power of two. Petya, on the other hand, is very conservative and only likes a single integer p (which may be positive, negative, or zero). To combine their tastes, they invented p -binary numbers of the form 2^x + p , where x is a non-negative integer. For example, some -9 -binary ("minus nine" binary) numbers are: -8 (minus eight), 7 and 1015 ( -8=2^0-9 , 7=2^4-9 , 1015=2^{10}-9 ). The boys now use p -binary numbers to represent everything. They now face a problem: given a positive integer n , what 's the smallest number of p -binary numbers (not necessarily distinct) they need to represent n as their sum? It may be possible that representation is impossible altogether. Help them solve this problem. For example, if p=0 we can represent 7 as 2^0 + 2^1 + 2^2 . And if p=-9 we can represent 7 as one number (2^4-9) . Note that negative p -binary numbers are allowed to be in the sum (see the Notes section for an example). The only line contains two integers n and p ( 1 <= q n <= q 10^9 , -1000 <= q p <= q 1000 ). If it is impossible to represent n as the sum of any number of p -binary numbers, print a single integer -1 . Otherwise, print the smallest possible number of summands. 0 -binary numbers are just regular binary powers, thus in the first sample case we can represent 24 = (2^4 + 0) + (2^3 + 0) . In the second sample case, we can represent 24 = (2^4 + 1) + (2^2 + 1) + (2^0 + 1) . In the third sample case, we can represent 24 = (2^4 - 1) + (2^2 - 1) + (2^2 - 1) + (2^2 - 1) . Note that repeated summands are allowed. In the fourth sample case, we can represent 4 = (2^4 - 7) + (2^1 - 7) . Note that the second summand is negative, which is allowed. In the fifth sample case, no representation is possible. '...