/*
  string s1; //构造一个空的string类对象 s1
  string s2="hello world"; //定义并初始化
  string s3("hello world"); //用C语言格式字符串构造string类对象
  string s4(10, 'a'); // 用10个字符'a'构造string对象s4
  string s5(s2); //拷贝构造s5
  string s6(s3,6); //用s3中下标为6开始的字符串构造string对象s6
 
 */

#include <iostream>
using namespace std;
int main()
{
  int a = 49, b=49;
  char c = 50;
  string s1 = "haha";
  string s2(s1);
  string s3("hello world");
  string s4(10, 'a');
  string s5(s2);
  string s6(s3,6);

  cin >> c >> a >> b;
  cout <<"hello world" << endl;
  printf("a:%c,b:%c\n",a,b);
  cout << "a:" << a << ",b:" << b << ",c:" << c << endl;

  cout << s1 << endl;
  cout << s2 << endl;
  cout << s3 << endl;
  cout << s4 << endl;
  cout << s5 << endl;
  cout << s6 << endl;
  
  return 0;    

}