Finding row index an element in cell array

How to find the row index of an element in a cell array if the cell array is non uniform like this:

 c=
 1
[6,7]
6
7
7

i.e if one asks for row index of 7, it should give 2,4,5 as answer. I tried using this: index=find([C{:}] == 7) but it gave 3,5,6 counting 6 and 7 in row 2 separately

Answer 1

[Guillaume]

find(cellfun(@(subc) ismember(7, subc), c))

[Hari]

It worked. Thank you