mod = 1000000007
eps = 10**-9


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

    N = int(input())
    A = list(map(int, input().split()))
    c = 0
    for a in A:
        c |= a
    for i in range(70):
        if not c >> i & 1:
            print(1 << i)
            break


if __name__ == '__main__':
    main()