#include <string>
using namespace std;
int main() {
string s1; // define an empty string
string s2 = "hello world"; // define a string with content
int sz = s2.size(); // assign size of string s2 to variable
char a = s2[1]; // access second character of s2 ('e')
string s3 = s2 + s2; // concatenate s2 with itself
bool b = s2.empty(); // true if s2 is an empty string
return 0;