STL string find substring

#include <iostream>
using namespace std;
//#pragma warning(disable:4996)// Remove warning 4996
void StrFunction()
{
    string str2("aabasasaaqde");
    string str3("aaq");
    // find function .
    cout << str2.find(str3, 7)<<endl;// Find and str3 The same string ,str2 Subscript is 7.
    cout << str2.find(str3, 8)<<endl;//find Returns an unsigned integer .
    cout << (int)str2.find(str3, 8)<<endl;//find Returns an unsigned integer .
    cout << str2.find("aaq", 2) << endl;
    cout << str2.find('a', 2) << endl;

    cout << str2.substr(2,4) << endl;// Returns the string from the subscript 2 Start （ Add subscript 2） There are four characters in total .

    str2.swap(str3);
    cout << str2<<endl;//str2 And str3 swapping .
    cout << str2+str3<<endl;//str2 And str3 Add up .
    cout << str2+"sjdhj" << endl;//str2 And str3 Add up .

}

int main()
{
    StrFunction();
    system("pause");
    return 0;
}