#D1956. Cut and Paste
Cut and Paste
Cut and Paste
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 ℓ is denoted by an integer in {0, …, |s|}, with the following meaning:
- If ℓ = 0, then the cursor is located before the first character of s.
- If ℓ = |s|, then the cursor is located right after the last character of s.
- If 0 < ℓ < |s|, then the cursor is located between s_ℓ and s_{ℓ+1}.
We denote by s_left the string to the left of the cursor and s_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 ℓ once.
- The Cut action. Set c ← s_right, then set s ← s_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 ℓ = 0. Then, we perform the following procedure:
- Perform the Move action once.
- Perform the Cut action once.
- Perform the Paste action s_ℓ times.
- If ℓ = 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 ℓ ≤ |s| at any time.
Input
The first line of input contains a single integer t (1 ≤ t ≤ 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 ≤ x ≤ 10^6). The second line of each test case consists of the initial string s (1 ≤ |s| ≤ 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 ℓ ≤ |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.
Example
Input
4 5 231 7 2323 6 333 24 133321333
Output
25 1438 1101 686531475
Note
Let's illustrate what happens with the first test case. Initially, we have s = 231. Initially, ℓ = 0 and c = \varepsilon (the empty string). The following things happen if we follow the procedure above:
-
Step 1, Move once: we get ℓ = 1.
-
Step 2, Cut once: we get s = 2 and c = 31.
-
Step 3, Paste s_ℓ = 2 times: we get s = 23131.
-
Step 4: ℓ = 1 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 2.
-
Step 2, Cut once: we get s = 23 and c = 131.
-
Step 3, Paste s_ℓ = 3 times: we get s = 23131131131.
-
Step 4: ℓ = 2 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 3.
-
Step 2, Cut once: we get s = 231 and c = 31131131.
-
Step 3, Paste s_ℓ = 1 time: we get s = 23131131131.
-
Step 4: ℓ = 3 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 4.
-
Step 2, Cut once: we get s = 2313 and c = 1131131.
-
Step 3, Paste s_ℓ = 3 times: we get s = 2313113113111311311131131.
-
Step 4: ℓ = 4 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 5.
-
Step 2, Cut once: we get s = 23131 and c = 13113111311311131131.
-
Step 3, Paste s_ℓ = 1 times: we get s = 2313113113111311311131131.
-
Step 4: ℓ = 5 = x, so we stop.
At the end of the procedure, s has length 25.
inputFormat
Input
The first line of input contains a single integer t (1 ≤ t ≤ 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 ≤ x ≤ 10^6). The second line of each test case consists of the initial string s (1 ≤ |s| ≤ 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 ℓ ≤ |s| at any time.
outputFormat
Output
For each test case, output a single line containing a single integer denoting the answer for that test case modulo 10^9 + 7.
Example
Input
4 5 231 7 2323 6 333 24 133321333
Output
25 1438 1101 686531475
Note
Let's illustrate what happens with the first test case. Initially, we have s = 231. Initially, ℓ = 0 and c = \varepsilon (the empty string). The following things happen if we follow the procedure above:
-
Step 1, Move once: we get ℓ = 1.
-
Step 2, Cut once: we get s = 2 and c = 31.
-
Step 3, Paste s_ℓ = 2 times: we get s = 23131.
-
Step 4: ℓ = 1 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 2.
-
Step 2, Cut once: we get s = 23 and c = 131.
-
Step 3, Paste s_ℓ = 3 times: we get s = 23131131131.
-
Step 4: ℓ = 2 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 3.
-
Step 2, Cut once: we get s = 231 and c = 31131131.
-
Step 3, Paste s_ℓ = 1 time: we get s = 23131131131.
-
Step 4: ℓ = 3 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 4.
-
Step 2, Cut once: we get s = 2313 and c = 1131131.
-
Step 3, Paste s_ℓ = 3 times: we get s = 2313113113111311311131131.
-
Step 4: ℓ = 4 not= x = 5, so we return to step 1.
-
Step 1, Move once: we get ℓ = 5.
-
Step 2, Cut once: we get s = 23131 and c = 13113111311311131131.
-
Step 3, Paste s_ℓ = 1 times: we get s = 2313113113111311311131131.
-
Step 4: ℓ = 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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