P3694 BanG Dream!'s Mass Chorus Lineup

All idol bands in BanG Dream! are going to sing a chorus together, but there are some issues with the lineup.

There are $N$ idols standing in a line, coming from $M$ different bands. Each band has at least one idol. We want to rearrange the line so that idols from the same band stand together contiguously. The way to rearrange is: let some idols leave the line (the remaining idols do not move), then let the removed idols return one by one to fill the vacated positions; they may return to any empty positions. What is the minimum number of idols that must leave the line?

The first line contains $2$ integers $N$ and $M$. Then there are $N$ lines, each containing an integer $a_i(1\le a_i \le M)$, representing the band ID of the $i$-th idol in the line.

Output a single integer, the answer.

Sample explanation: ```cpp 1 3 √ 3 3 2 3 √ 4 4 2 4 √ 1 2 √ 2 2 3 2 √ 1 1 1 1 3 1 √ 4 1 √ ``` Constraints: - For $20\%$ of the testdata, $N\le 20, M=2$. - For $40\%$ of the testdata, $N\le 100, M\le 4$. - For $70\%$ of the testdata, $N\le 2000, M\le 10$. - For all testdata, $1\le N\le 10^5, M\le 20$. Translated by ChatGPT 5