CSES - Required Substring
  • Time limit: 1.00 s
  • Memory limit: 512 MB
Your task is to calculate the number of strings of length $n$ having a given pattern of length $m$ as their substring. All strings consist of characters A–Z.

Input

The first input line has an integer $n$: the length of the final string.

The second line has a pattern of length $m$.

Output

Print the number of strings modulo $10^9+7$.

Constraints
  • $1 \le n \le 1000$
  • $1 \le m \le 100$
Example

Input:
6
ABCDB


Output:
52

Explanation: The final string will be of the form ABCDB$x$ or $x$ABCDB where $x$ is any character between A–Z.