A11343. Following the String

Polycarp lost the string $s$ of length $n$ consisting of lowercase Latin letters, but he still has its trace.

The trace of the string $s$ is an array $a$ of $n$ integers, where $a_i$ is the number of such indices $j$ ( $j < i$ ) that $s_i=s_j$ . For example, the trace of the string abracadabra is the array \[ $0, 0, 0, 1, 0, 2, 0, 3, 1, 1, 4$ \].

Given a trace of a string, find any string $s$ from which it could have been obtained. The string $s$ should consist only of lowercase Latin letters a-z.

The first line of the input contains a single integer $t$ ( $1 \le t \le 10^4$ ) — the number of test cases. Then the descriptions of the test cases follow.

The first line of each test case contains a single integer $n$ ( $1 \le n \le 2 \cdot 10^5$ ) — the length of the lost string.

The second line of each test case contains $n$ integers $a_1, a_2, \dots, a_n$ ( $0 \le a_i < n$ ) — the trace of the string. It is guaranteed that for the given trace, there exists a suitable string $s$ .

It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^5$ .

For each test case, output a string $s$ that corresponds to the given trace. If there are multiple such strings $s$ , then output any of them.

The string $s$ should consist of lowercase Latin letters a-z.

It is guaranteed that for each test case, a valid answer exists.