You are given n string S1,S2,...,Sn.
Find the shortest string S that S1,S2,...,Sn are substrings of S.
### Input
- The first line contains an integer n.
- The next n lines, each line contains a string Si.
### Output
- Print the shortest string.
### Constraints
- 1≤n≤20.
- 1≤|Si|≤100.
### Example
Input:
3abbda
Output:
dab
