第10题

#include <iostream>
#include <string>
using namespace std;
int main()
{ string string1="abc";
  string string2="def";
  cout<<"string1="<<string1<<endl;
  cout<<"string2="<<string2<<endl;
  string1=string1+string2;
  cout<<"The new string is:"<<string1<<endl;
  return 0;
}