# //Given a string s, consider all duplicated substrings: (contiguous) substrings of s that occur 2 or more times. The occurrences may overlap.

# //Return any duplicated substring that has the longest possible length. If s does not have a duplicated substring, the answer is "".

# //Example 1:

# //Input: s = "banana"
# //Output: "ana"
# //Example 2:

# //Input: s = "abcd"
# //Output: ""
