from collections import Counter
N=int(input())
A=[]
for _ in range(N):
    A.append(int(input()))
A.sort()
D=[]
for i in range(1,N):
    D.append(A[i]-A[i-1])
C=Counter(D)
if C[1]==0:
    print(1)
elif C[1]>=1:
    print(2)