CF1148F Foo Fighters

You are given $ n $ objects. Each object has two integer properties: $ val_i $ — its price — and $ mask_i $ . It is guaranteed that the sum of all prices is initially non-zero. You want to select a positive integer $ s $ . All objects will be modified after that. The $ i $ -th object will be modified using the following procedure: - Consider $ mask_i $ and $ s $ in binary notation, - Compute the [bitwise AND](https://en.wikipedia.org/wiki/Bitwise_operation#AND) of $ s $ and $ mask_i $ ( $ s \,\&\, mask_i $ ), - If ( $ s \,\&\, mask_i $ ) contains an odd number of ones, replace the $ val_i $ with $ -val_i $ . Otherwise do nothing with the $ i $ -th object. You need to find such an integer $ s $ that when the modification above is done the sum of all prices changes sign (if it was negative, it should become positive, and vice-versa; it is not allowed for it to become zero). The absolute value of the sum can be arbitrary.

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In the first test sample all objects will change their prices except for the object with mask $ 151 $ . So their total sum will change its sign: initially $ 24 $ , after modifications — $ -28 $ . In the second test sample the only object will change its price. So the total sum will change its sign.