string concatenation with +

One of the most delightful discoveries awaiting a C programmer learning about C++ string handling is how simply strings can be combined and appended using operator+ and
operator+=. These operators make combining strings syntactically equivalent to adding numeric data. Example :

#include <string>
#include <iostream>
using namespace std;
int main() 
    string s1("Humpty ");
    string s2("Dumpty ");
    string s3(", then what i do ? ");
    // operator+ concatenates strings
    s1 = s1 + s2;
    cout << s1 << endl;
    // Another way to concatenates strings
    s1 += s3;
    cout << s1 << endl;
    // You can index the string on the right
    s1 += s3 + s3[4] + "hahaha";
    cout << s1 << endl;
    return 0;