Does anyone know how to lookup a value in following example?

[A1] 1 [B1] 45
[A2] 2 [B2] 90
[A3] 3 [B3] 88
[A4] 4 [B4] 56

I would like to look up the highest value under B colume, such as 90 in cell
B2 in this case, and return the value of 2 from cell A2 into C1 cell.
Does anyone have any suggestion?
Thank you very much
Eric