填空题

下列程序的输出结果是______。
#include ＜iostream＞
using namespace std;
class base
public:
int n;
base(int x) n=x;
virtual void set(int m) n=m; cout＜＜n＜＜’ ’;
;
class deriveA :public base
public:
deriveA(int x):base(x)
void set(int m) n+=m; cout＜＜n＜＜’ ’;
;
class derive B: public base
public:
derive B(int x):base(x)
void set(int m) n+=m; cout＜＜n＜＜’ ’;
;
int main() derive A, d1(1);
derive B, d2(3);
base *pbase;
pbase=&d1;
pbase-＞set(1);
pbase=&d2;
phase-＞set(2);
return 0;

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