C++异常处理机制----C++primer4

#include<iostream>
#include<stdexcept>
#include<exception>
using namespace std;

int main()
{
    int a,b;
    a=-3;
    b=2;
    try
    {
        if((a+b)<0)
            throw runtime_error("have something wrong!!!");
        cout<<a+b<<endl;
    }
    catch(runtime_error err )
    {  
        cout<< err.what();
        cout<<a<<‘ ‘<<b<<endl;
    }

    system("pause");
    return 1;
}