Does anyone have any suggestions on how to determine the closeest number?

Example One
There is a list of number under column A
191,189,183,177,175,171,167,165,159,153,151
and there is a given number in cell B1, 154.
I would like to determine the closest number, which match with the number in
cell B1. On above example, it should return 153 in cell C1.

Example Two
There is a list of number under column A
191,189,183,177,175,171,167,165,155,153,151
and there is a given number in cell B1, 154.
I would like to determine the closest number, which match with the number in
cell B1. On above example, if the given number matches two numbers, which the
difference is the same, then it should return 153 in cell C1.
Does anyone have any suggestions?
Thanks in advance for any suggestions
Eric