import sys
sys.setrecursionlimit(1000000000)

#
# Solution Template for Subbookkeeper
# 
# Australian Informatics Olympiad 2024
# 
# This file is provided to assist with reading of input and writing of output
# for the problem. You may modify this file however you wish, or
# you may choose not to use this file at all.
#

# N is the number of letters in the word.
N = 0

# word is the word with one missing letter
word = ""

# Read the value of N and the word.
N = int(input().strip())
word = input().strip()

# TODO: This is where you should compute your solution. Store the largest score
# that Rebecca can achieve into the variable answer.

answer = 0

# Write the answer.
print(answer)