#from statistics import median

#import collections

#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]

from fractions import gcd

from itertools import combinations,permutations,accumulate # (string,3) 3回

#from collections import deque

from collections import deque,defaultdict,Counter

import decimal

import re

#import bisect

#

#    d = m - k[i] - k[j]

#    if kk[bisect.bisect_right(kk,d) - 1] == d:

#

#

#

# pythonで無理なときは、pypyでやると正解するかも！！

#

#

# my_round_int = lambda x:np.round((x*2 + 1)//2)

# 四捨五入

import sys

sys.setrecursionlimit(10000000)

mod = 10**9 + 7

#mod = 9982443453

def readInts():

  return list(map(int,input().split()))

def I():

  return int(eval(input()))

n = I()

s = eval(input())

t = eval(input())

same = 0

for i in range(n):

    #print(s[n-i-1:], t[:i+1])

    if s[n-i-1:] == t[:i+1]:

        same = i+1

print((len(s) + len(t) - same))

#from statistics import median

#import collections

#aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]

from fractions import gcd

from itertools import combinations,permutations,accumulate, product # (string,3) 3回

#from collections import deque

from collections import deque,defaultdict,Counter

import decimal

import re

#import bisect

#

#    d = m - k[i] - k[j]

#    if kk[bisect.bisect_right(kk,d) - 1] == d:

#

#

#

# pythonで無理なときは、pypyでやると正解するかも！！

#

#

# my_round_int = lambda x:np.round((x*2 + 1)//2)

# 四捨五入g

import sys

sys.setrecursionlimit(10000000)

mod = 10**9 + 7

#mod = 9982443453

def readInts():

  return list(map(int,input().split()))

def I():

  return int(eval(input()))

n = I()

s = eval(input())

t = eval(input())

if s == t:

    print(n)

    exit()

for i in range(n):

    if s[i:] == t[:-i]:

        print((n+i))

        exit()

print((n+n))

# from statistics import median
# import collections
# aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from fractions import gcd
from itertools import combinations, permutations, accumulate  # (string,3) 3回

# from collections import deque
from collections import deque, defaultdict, Counter
import decimal
import re

# import bisect
#
#    d = m - k[i] - k[j]
#    if kk[bisect.bisect_right(kk,d) - 1] == d:
#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#
# my_round_int = lambda x:np.round((x*2 + 1)//2)
# 四捨五入
import sys

sys.setrecursionlimit(10000000)
mod = 10**9 + 7
# mod = 9982443453
def readInts():
    return list(map(int, input().split()))


def I():
    return int(eval(input()))


n = I()
s = eval(input())
t = eval(input())
same = 0
for i in range(n):
    # print(s[n-i-1:], t[:i+1])
    if s[n - i - 1 :] == t[: i + 1]:
        same = i + 1
print((len(s) + len(t) - same))

# from statistics import median
# import collections
# aa = collections.Counter(a) # list to list || .most_common(2)で最大の2個とりだせるお a[0][0]
from fractions import gcd
from itertools import combinations, permutations, accumulate, product  # (string,3) 3回

# from collections import deque
from collections import deque, defaultdict, Counter
import decimal
import re

# import bisect
#
#    d = m - k[i] - k[j]
#    if kk[bisect.bisect_right(kk,d) - 1] == d:
#
#
#
# pythonで無理なときは、pypyでやると正解するかも！！
#
#
# my_round_int = lambda x:np.round((x*2 + 1)//2)
# 四捨五入g
import sys

sys.setrecursionlimit(10000000)
mod = 10**9 + 7
# mod = 9982443453
def readInts():
    return list(map(int, input().split()))


def I():
    return int(eval(input()))


n = I()
s = eval(input())
t = eval(input())
if s == t:
    print(n)
    exit()
for i in range(n):
    if s[i:] == t[:-i]:
        print((n + i))
        exit()
print((n + n))

-from itertools import combinations, permutations, accumulate  # (string,3) 3回 +from itertools import combinations, permutations, accumulate, product  # (string,3) 3回 -# 四捨五入 +# 四捨五入g -same = 0 +if s == t: +    print(n) +    exit() -    # print(s[n-i-1:], t[:i+1]) -    if s[n - i - 1 :] == t[: i + 1]: -        same = i + 1 -print((len(s) + len(t) - same)) +    if s[i:] == t[:-i]: +        print((n + i)) +        exit() +print((n + n))