n = int(input())
a = list(map(int, input().split()))

# Calculate the maximum frequency of any value in the array
from collections import defaultdict
count = defaultdict(int)
for num in a:
    count[num] += 1
max_freq = max(count.values()) if count else 0

# Calculate the maximum non-adjacent selection using dynamic programming
if n == 0:
    max_independent = 0
elif n == 1:
    max_independent = 1
else:
    prev_not = 0  # Represents not taking the previous element
    prev_yes = 1  # Represents taking the previous element
    for i in range(1, n):
        current_not = max(prev_not, prev_yes)
        current_yes = prev_not + 1
        prev_not, prev_yes = current_not, current_yes
    max_independent = max(prev_not, prev_yes)

# The answer is the maximum of the two strategies
print(max(max_freq, max_independent))