[20, -7, -2, 1, 8, 12, -20]
Result: 1
[1, -2, 7, -15, 4]
Result: 1
[-8, -100, -7, -1, -2]
Result: -1
[2, -2]
Result: -2
[1, 1]
Result: 1
null
Result: 0
[]
Result: 0
[99, 102, 2, 0, 1, 3, 6]
Result: 0
[99, 102, 200, 1000, 300, 600, -99]
Result: -99