【2019 南昌网络赛】Hello 2019（线段树、矩阵、dp）
A digital string is “good”: when it contains a subsequence 91029102 and does not contain a subsequence 81028102.
The bad value of a string is defined as how many characters are to remove at least, so that the string satisfies the “good” property. Output -1 if the string cannot satisfy the “good” property by removing some characters (0 or maybe more).
Input
The first line contains two integers n , Q ( 1 ≤ n , Q ≤ 2 ∗ 1 0 5 ) n,Q(1\leq n,Q\leq2*10^5) n,Q(1≤n,Q≤2∗105) n is the length of the string and Q is the number of queries.
The second line contains a string s that consists entirely of decimal numbers.
The next Q line, each line contains two integers l , r ( 1 ≤ l ≤ r ≤ n ) l,r(1≤l≤r≤n) l,r(1≤l≤r≤n), denoting a query.
Output
For each query, output an answer which is the bad value of the substring s l s l + 1 ⋯ s r s_ls_{l+1} \cdots s_r slsl+1⋯srfrom s.
样例输入
8 3
88988102
1 8
2 8
1 7
样例输出
4
3
-1
代码：
#include