#include <iostream>
#include <string>

int main() {
    std::string s { "abcdef" };
    const auto it1 = std::begin(s);
    const auto it2 = std::begin(s);
    std::cout << (*it2) << std::endl;
    (*it1) = 'A';
    std::cout << (*it2) << std::endl;
}