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)

Scanf.scanf "%d %s %s" (fun n s t ->
    let rec loop dup =
        if dup = 0 then dup else
            let rec loop2 a b =
                if b < 0 then dup else
                    if s.[a] = t.[b] then loop2 (a - 1) (b - 1)
                    else loop (dup - 1)
            in
            loop2 (n - 1) (dup - 1)
    in
    let dup = loop n in
    Printf.printf "%d\n" (n * 2 - dup)
)