import sys
input = sys.stdin.readline

def main():
    N = int(input())
    A = list(map(int,input().split()))
    MAX = 70
    ans = 0
    for j in range(MAX):
        for i in range(N):
            if (A[i]>>j)&1 == 1: break
        else:
            ans += 1<<j
            break
    print(ans)
        

if __name__ == '__main__':
    main()