Given $n$ sequences, each containing $m$ elements, choose exactly one element from each sequence such that the difference between the largest and smallest chosen elements is minimized.
### Input
- The first line contains two integers $n$ and $m$.
- The next $n$ lines each contain $m$ integers, representing a sequence.
### Output
- Print a single integer, the minimum possible difference between the largest and smallest chosen elements.
### Constraints
- $1 \leq n, m \leq 1000$.
- The absolute value of the numbers in the sequences does not exceed $10^9$.
### Example
Input:
```
3 4
12 16 67 43
7 17 68 48
14 15 77 54
```
Output:
```
2
```
