有以下程序: #included<iostream> using namespace std; class Base public: Base( ) x=0; int x; ; class Derived1:virtual public Base public: Derived1( ) x=10; ; class Derived2:virtual public Base public: Derived2( ) x=20; ; class Derived: public Derived1,protected Derived2 ; int main( ) Derived obj; cout<<obj. x<<endl; return 0; 该程序运行后的输出结果是______。