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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

import           Control.Monad
import qualified Data.ByteString.Char8 as BS
import           Data.Maybe
import qualified Data.Sequence         as Seq

readInt = fst . fromJust . BS.readInt
getInt = readInt <$> BS.getLine

main = do
  n <- getInt
  s <- Seq.fromList <$> getLine
  t <- Seq.fromList <$> getLine

  let solve i | i == n    = 2*n
              | otherwise =
                 let bs = Seq.drop i s
                     bt = Seq.take (n-i) t
                 in if bs == bt
                    then n+i
                    else solve (i+1)

  print $ solve 0