missingSevens.js

/** 
$ missingSevens([[9,4,3],[3,4,9],[4,8,4]])
$ 0

9 4 3
3 4 9
4 8 4

$ missingSevens([[1,5,2],[5,9,5],[6,5,3]])
$ 4

$ missingSevens([[3,9,6],[8,5,5],[8,4,0]])
$ 2
 */