Output Format

Output the minimum number of lifts needed.

9 3
1 1 1 2 2 2 1 1 1
1 2 1 2 3 2 1 2 1
1 1 1 2 2 2 1 1 1

3

Hint

Constraints: $1 \le W, L \le 500$, $0 \le H \le 9999$.

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