Problem:
Score : 200 points

Problem Statement

Snuke is interested in strings that satisfy the following conditions:

The length of the string is at least N.

The first N characters equal to the string s.

The last N characters equal to the string t.

Find the length of the shortest string that satisfies the conditions.

Constraints

1≤N≤100

The lengths of s and t are both N.

s and t consist of lowercase English letters.

Input

The input is given from Standard Input in the following format:

N
s
t

Output

Print the length of the shortest string that satisfies the conditions.

Sample Input 1

3
abc
cde

Sample Output 1

5

The shortest string is abcde.

Sample Input 2

1
a
z

Sample Output 2

2

The shortest string is az.

Sample Input 3

4
expr
expr

Sample Output 3

4

The shortest string is expr.

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let () =
	let n = read_int () in
	let s = read_line () in
	let t = read_line () in
	let rec loop s t n =
		if n = 0 then 0
		else if Str.last_chars s n = Str.first_chars t n then n
		else loop s t (n - 1)
	in
	loop s t n
	|> ( - ) (n * 2)
	|> print_int
	|> print_newline