import numpy as np


def main():
    N = int(input())
    A = [int(input()) for _ in range(N)]
    A.sort()
    if N == 1:
        print(1)
        return

    A_array = np.array(A[:-1])
    A_array_slide = np.array(A[1:])
    diff = A_array_slide - A_array
    if 1 in diff:
        print(2)
    else:
        print(1)


if __name__ == "__main__":
    main()