CF1914A.Problemsolving Log

Monocarp is participating in a programming contest, which features $26$ problems, named from 'A' to 'Z'. The problems are sorted by difficulty. Moreover, it's known that Monocarp can solve problem 'A' in $1$ minute, problem 'B' in $2$ minutes, ..., problem 'Z' in $26$ minutes.

After the contest, you discovered his contest log — a string, consisting of uppercase Latin letters, such that the $i$-th letter tells which problem Monocarp was solving during the $i$-th minute of the contest. If Monocarp had spent enough time in total on a problem to solve it, he solved it. Note that Monocarp could have been thinking about a problem after solving it.

Given Monocarp's contest log, calculate the number of problems he solved during the contest.

Monocarp 正在参加一场编程竞赛，该竞赛共有 $26$ 道题目，分别命名为 'A' 到 'Z'。这些题目按难度递增排序。此外，已知 Monocarp 解决题目 'A' 需要 $1$ 分钟，解决题目 'B' 需要 $2$ 分钟，……，解决题目 'Z' 需要 $26$ 分钟。

比赛结束后，你发现了他的比赛日志——一个由大写拉丁字母组成的字符串，其中第 $i$ 个字母表示 Monocarp 在比赛的第 $i$ 分钟正在思考哪道题。如果 Monocarp 在某道题上累计花费的时间不少于其解决所需时间，则他成功解决了该题。注意：Monocarp 可能在解出某道题后仍继续思考该题。

给定 Monocarp 的比赛日志，请计算他在比赛中成功解决的题目数量。

The first line contains a single integer $t$ ($1 \le t \le 100$) — the number of testcases.

The first line of each testcase contains a single integer $n$ ($1 \le n \le 500$) — the duration of the contest, in minutes.

The second line contains a string of length exactly $n$, consisting only of uppercase Latin letters, — Monocarp's contest log.

第一行包含一个整数 $t$（$1 \le t \le 100$）——测试用例的数量。

每个测试用例的第一行包含一个整数 $n$（$1 \le n \le 500$）——比赛的持续时间（单位：分钟）。

每个测试用例的第二行包含一个长度恰好为 $n$ 的字符串，该字符串仅由大写拉丁字母组成——Monocarp 的比赛日志。

For each testcase, print a single integer — the number of problems Monocarp solved during the contest.

对于每个测试用例，输出一个整数——Monocarp 在比赛期间解决的问题数量。