# https://yukicoder.me/problems/no/1219

from collections import deque

def main():
    N = int(input())
    A = list(map(int, input().split()))

    answer = 0
    for k in range(40):
        x = 2 ** k
        count = [0, 0]
        for a in A:
            if (1 << k) & a > 0:
                count[1] += 1
            else:
                count[0] += 1

        if count[0] > 0 and count[1] > 0:
            answer += x
    print(answer)





if __name__ == "__main__":
    main()