std::string

#include <cstdio>
#include <iostream>
#include <string> // library for string data type

using namespace std;
// necessary in order to work with any C++library
// (in that case, with <string> and <iostream>)

int main() {
    string s = "";
    /* creates empty string.
    One can initialize the string with any value.
    E.g.:
    string s = "abacaba";
    */

    for (char i = 'a'; i <= 'z'; i++)
        s += i;
    /* Adds symbols in alphabitical order.

    Attention!

    += works with complexity in proportion
    to the size of the part we add

    + (s = s + i) works in proportion
    to the total size of the string we obtain
    after addition

    So,
    for (int i = 0; i < int(1e5); i++)
        s = s + 'a';
    leads to TL,

    but
    for (int i = 0; i < int(1e5); i++)
        s += 'a';
    doesn't.

    */

    cout << s.size() << endl; // outputs string length
    cout << s.length() << endl; // the same as the previous one command

    int cnt_less_n = 0;
    for (int i = 0; i < s.size(); i++) {
        // shows how one can get i-th symbol of the string (0 <= i < s.size())
        if (s[i] < 'n') // comparison of two symbols (by their codes)
            cnt_less_n++;
    }
    cout << cnt_less_n << " symbols less than n in " << s << endl;

    // first parameter = index of the leading symbol in the substring
    // second parameter = length of substring
    cout << s.substr(3, 5) << endl;

    // if one need to get some suffix of the string,
    // he is permitted to omit the second parameter
    cout << s.substr(3) << endl;

    return 0;
}