Display all values in other cells with no duplicates
 

Please see the example below. What would be the formula to display in one
cell, A5 all the values in A1:D2 without any duplicates. Thanks in advance.

Example

A B C D
1) 1 6 3 7
2) 2 7 6 5
3)
4)
5) 1,2,3,5,6,7