填空题

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______。

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