Subset sum problem
The subset sum problem is an important problem of computer science. It can be stated as follows: Given a set of integers, does any subset of them sum to zero?  For example, given the set { -7, -3, -2, 5, 8}, the answer is yes because the subset { -3, -2, 5} sums to zero.  The problem is NP-Complete. It can be reformulated to the 3SAT.