mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.buffer.readline

    N = int(input())
    A = []
    for _ in range(N):
        A.append(int(input()))
    A.sort()
    ans = 1
    for i in range(N-1):
        if A[i] + 1 == A[i+1]:
            ans += 1
            break
    print(ans)


if __name__ == '__main__':
    main()