We start with a string $s$ consisting only of the digits $1$, $2$, or $3$. The length of $s$ is denoted by $|s|$. For each $i$ from $1$ to $|s|$, the $i$-th character of $s$ is denoted by $s_i$.
There is one cursor. The cursor's location $\ell$ is denoted by an integer in $\{0, \ldots, |s|\}$, with the following meaning:
- If
$\ell = 0$, then the cursor is located before the first character of$s$. - If
$\ell = |s|$, then the cursor is located right after the last character of$s$. - If
$0 \lt \ell \lt |s|$, then the cursor is located between$s_\ell$and$s_{\ell+1}$.
We denote by $s_\text{left}$ the string to the left of the cursor and $s_\text{right}$ the string to the right of the cursor.
We also have a string $c$, which we call our clipboard, which starts out as empty. There are three types of actions:
- The Move action. Move the cursor one step to the right. This increments
$\ell$once. - The Cut action. Set
$c \leftarrow s_\text{right}$, then set$s \leftarrow s_\text{left}$. - The Paste action. Append the value of
$c$to the end of the string$s$. Note that this doesn't modify$c$.
The cursor initially starts at $\ell = 0$. Then, we perform the following procedure:
- Perform the Move action once.
- Perform the Cut action once.
- Perform the Paste action
$s_\ell$times. - If
$\ell = x$, stop. Otherwise, return to step 1.
You're given the initial string $s$ and the integer $x$. What is the length of $s$ when the procedure stops? Since this value may be very large, only find it modulo $10^9 + 7$.
It is guaranteed that $\ell \le |s|$ at any time.
Input
The first line of input contains a single integer $t$ ($1 \le t \le 1000$) denoting the number of test cases. The next lines contain descriptions of the test cases.
The first line of each test case contains a single integer $x$ ($1 \le x \le 10^6$). The second line of each test case consists of the initial string $s$ ($1 \le |s| \le 500$). It is guaranteed, that $s$ consists of the characters "1", "2", "3".
It is guaranteed that the sum of $x$ in a single file is at most $10^6$. It is guaranteed that in each test case before the procedure will stop it will be true that $\ell \le |s|$ at any time.
Output
For each test case, output a single line containing a single integer denoting the answer for that test case modulo $10^9 + 7$.
Note
Let's illustrate what happens with the first test case. Initially, we have $s = $ 231. Initially, $\ell = 0$ and $c = \varepsilon$ (the empty string). The following things happen if we follow the procedure above:
- Step 1, Move once: we get
$\ell = 1$. - Step 2, Cut once: we get
$s = $2and$c = $31. - Step 3, Paste
$s_\ell = $2times: we get$s = $23131. - Step 4:
$\ell = 1 \not= x = 5$, so we return to step 1. - Step 1, Move once: we get
$\ell = 2$. - Step 2, Cut once: we get
$s = $23and$c = $131. - Step 3, Paste
$s_\ell = $3times: we get$s = $23131131131. - Step 4:
$\ell = 2 \not= x = 5$, so we return to step 1. - Step 1, Move once: we get
$\ell = 3$. - Step 2, Cut once: we get
$s = $231and$c = $31131131. - Step 3, Paste
$s_\ell = $1time: we get$s = $23131131131. - Step 4:
$\ell = 3 \not= x = 5$, so we return to step 1. - Step 1, Move once: we get
$\ell = 4$. - Step 2, Cut once: we get
$s = $2313and$c = $1131131. - Step 3, Paste
$s_\ell = $3times: we get$s = $2313113113111311311131131. - Step 4:
$\ell = 4 \not= x = 5$, so we return to step 1. - Step 1, Move once: we get
$\ell = 5$. - Step 2, Cut once: we get
$s = $23131and$c = $13113111311311131131. - Step 3, Paste
$s_\ell = $1times: we get$s = $2313113113111311311131131. - Step 4:
$\ell = 5 = x$, so we stop.
At the end of the procedure, $s$ has length $25$.
样例
4
5
231
7
2323
6
333
24
133321333
25
1438
1101
686531475
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