def yukicoder1285(N, A):
    A = sorted(A)
    ans = 1
    for i in range(1, N):
        if A[i] - A[i - 1] == 1:
            ans = 2
            break
    return ans



N = int(input())
A = [int(input()) for _ in range(N)]
print(yukicoder1285(N, A))