#xor minimax
def main():
    N = int(input())
    a = list(map(int, input().split()))
    a.sort()
    def solve(order, l, r):
        if order == -1:
            return 0
        if l > r:
            return 10**20
        
        if l == r:
            return 0
        else:
            new_r = r + 1
            for i in range(l, r+1):
                if (a[i]>> order) & 1:
                    new_r = i
                    break
         
            if l < new_r < r + 1:
                return min(solve(order-1, l, new_r-1), solve(order-1, new_r, r)) + (1 << order)
            else:
                return solve(order-1, l, r)
                

    ans = solve(30, 0, N-1)
    print(ans)
    return


if __name__ == "__main__":
    main()