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Monk has a matrix of size $$N \times M$$, and he wants to pick one element from each row to make a new array $$A$$ of size $$N$$. He wants to find the minimum possible value of absolute difference between any two adjacent elements in the array $$A$$. Please note that the element picked from row $$1$$, will become $$A[1]$$, element picked from row $$2$$ will become $$A[2]$$, and so on.
Input:
First line consists of two space separated integers denoting $$N$$ and $$M$$.
Each of the following $$N$$ lines consists of $$M$$ space separated integers denoting the matrix $$mat$$.
Output:
Print the required answer in a new line.
Constraints:
$$2 \le N, M \le 1000$$
$$1 \le mat[i][j] \le 10^9$$
Minimum difference Monk can achieve is $$0$$ by choosing $$8$$ from both rows.