Array Operation with using another array

I have 2 different arrays as

k=[4 9 3 3 6 8 8 12 6]

m=[1 2 6 7]

i need to reach the summation of

k(1)+k(2)+k(6)+k(7)

how can i do this with for loop?

Answer 1

[Kevin Phung]

sum(k(m))