n = int(input())
l = [int(x) for x in input().split()]
l.sort()
t = 0
s = []
i = 0
while(i<n-1):
    s.append([l[i]])
    while(i<n-1):
        if(l[i+1] - min(s[len(s)-1]) <= 1):
            s[len(s)-1].append(l[i+1])
            i+=1
        else:
            i+=1
            break

print(max([len(i) for i in s]))