I have a table that resembles below:

G P R
1 8 10
1 4 11
2 3 12
2 7 13
3 8 14
3 4 15

G, P, and R are in columns a, b, and c starting in row 1.

I'm trying to use the equation below to take a person's entry of G (in e2)
and P (in f2) and return the R value, but it always returns an error.
=index(c2:c7,match(e2&f2,a2:a7&b2:b7,0))
Any advice?