import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N = I()
A = [I() for _ in range(N)]
A.sort()

ans = 1
r = A[0]
for i in range(1,N):
    if A[i] > r+1:
        ans += 1
        r = A[i]

if ans == N:
    print(1)
else:
    print(2)