i have data that looks like the following:

2   7
1   5
2   7
1   4
2   7

I need a formula that will find how many time the number 7 is in the right
column and add up the corresponding number in the left column.  So the answer
for this example would be 6, found 3 sevens in right column so added 2+2+2.
I tried an index(...,match(  but couldnt get it to work.  Please help.
Thanks.