from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    N = int(input())
    A = [int(input()) for _ in [0] * N]

    A.sort()
    ans = 1
    for i in range(1, N):
        if A[i] - A[i - 1] > 1:
            continue
        else:
            ans = 2
            break
    print(ans)


main()