B"You've got a positive integer sequence a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89an. All numbers in the sequence are distinct. Let's fix the set of variables b1, xe2 x80 x89b2, xe2 x80 x89..., xe2 x80 x89bm. Initially each variable bi (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89i xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m) contains the value of zero. Consider the following sequence, consisting of n operations. The first operation is assigning the value of a1 to some variable bx (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89x xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m). Each of the following n xe2 x80 x89- xe2 x80 x891 operations is assigning to some variable by the value that is equal to the sum of values that are stored in the variables bi and bj (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89i, xe2 x80 x89j, xe2 x80 x89y xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89m). At that, the value that is assigned on the t-th operation, must equal at. For each operation numbers y, xe2 x80 x89i, xe2 x80 x89j are chosen anew. Your task is to find the minimum number of variables m, such that those variables can help you perform the described sequence of operations. The first line contains integer n (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x8923). The second line contains n space-separated integers a1, xe2 x80 x89a2, xe2 x80 x89..., xe2 x80 x89an (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89ak xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89109). It is guaranteed that all numbers in the sequence are distinct. In a single line print a single number -- the minimum number of variables m, such that those variables can help you perform the described sequence of operations. If you cannot perform the sequence of operations at any m, print -1. In the first sample, you can use two variables b1 and b2 to perform the following sequence of operations."...