#include <string>

using namespace std;

​

int main(void)

{

    string str1, str2, str3;

    str1.append("C++ Programming");

    str2.append("C++ Programming", 4, 7);

    str3.append(4, 'X');

    cout << str1 << endl;

    cout << str2 << endl;

    cout << str3;

    return 0;

}