B'Pak Chanek is participating in a lemper cooking competition. In the competition, Pak Chanek has to cook lempers with N stoves that are arranged sequentially from stove 1 to stove N . Initially, stove i has a temperature of A_i degrees. A stove can have a negative temperature. Pak Chanek realises that, in order for his lempers to be cooked, he needs to keep the temperature of each stove at a non-negative value. To make it happen, Pak Chanek can do zero or more operations. In one operation, Pak Chanek chooses one stove i with 2 <= q i <= q N-1 , then: Pak Chanek wants to know the minimum number of operations he needs to do such that the temperatures of all stoves are at non-negative values. Help Pak Chanek by telling him the minimum number of operations needed or by reporting if it is not possible to do. The first line contains a single integer N ( 1 <= N <= 10^5 ) -- the number of stoves. The second line contains N integers A_1, A_2, ldots, A_N ( -10^9 <= q A_i <= q 10^9 ) -- the initial temperatures of the stoves. Output an integer representing the minimum number of operations needed to make the temperatures of all stoves at non-negative values or output -1 if it is not possible. For the first example, a sequence of operations that can be done is as follows: There is no other sequence of operations such that the number of operations needed is fewer than 4 . '...