n = raw_input()
a = map(int,raw_input().strip().split(' '))

int_map = [0] * 101

for num in a:
    int_map[num] += 1

max_nums = 0    

for i in xrange(len(int_map) - 1):
    current_max = int_map[i] + int_map[i + 1]
    max_nums = max(max_nums, current_max)

print max_nums