n = int(input())
A = [int(x) for x in input().split()]

count = 0
for i in range(0,n):
    localMax = 1
    for j in range(0,n):
        if i == j:
            continue
        diff = A[i] - A[j]
        if diff == 1 or diff == 0:
            localMax+=1
    if localMax > count:
        count = localMax
        
print(count)