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 Ruby (2.3.3) (judge verdict: Wrong Answer)

require 'pp'

# 入力値を数値で返却する
def gets_i()
  gets.chomp.to_i
end

# 入力値を文字の配列で返却する
def gets_nsp_list()
  gets.chomp.split("")
end

N = gets_i
s_list = gets_nsp_list
t_list = gets_nsp_list

if s_list.join == t_list.join
  puts s_list.size
  exit
end

s_list = s_list.reverse

count = 0
(0...N).each do |i|
  if s_list[i] == t_list[i]
    s_list.shift
    t_list.shift
    count += 1
  else
    puts s_list.size + t_list.size + count
    exit
  end
end