Search rows in a table with uneven rows

A B C D E F
1 A B C D E
2 40 5 15 25 30 40
3 50 0 10 15 25
4 60 0 10 15
5 70 0 5

user input 1 (refers to column A): 50
user input 2 (refers to a value in the table associated with user input1): 17

The table above is an example of that data I'm working with. What I want to do is, based upon user input1 and user input2, find the corresponding letter. In this example, user input1 is 50 so row 3 is selected. User input2 is 17. Find an equal or next largest value in row 3. That would be 25 and the corresponding letter is D.

I know how to do this with rows of equal length but not unequal.