namespace如何声明?

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
inline long long r_ll(){
	long long f=1,x=0;char c;
	do{c=getchar();if(c=='-')f=-1;}while(c<'0'||c>'9');
	do{x=x*10+c-'0';c=getchar();}while(c>='0'&&c<='9');
	return f*x; 
}
namespace A{
	int a,b;
	int work(){
		return B::a+b;
	}
}
namespace B{
	int a,b;
	int work(){
		return A::a+b;
	}
}
int main(){
	A::a=r_ll(),A::b=r_ll(),B::a=r_ll(),B::b=r_ll();
	printf("%d\n",A::work());
	printf("%d\n",B::work());
	return ; 
}