#include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <locale>

int main()
{
    std::string a = "ABC";

    std::transform(a.begin(), a.end(), a.begin(), 
        std::bind2nd(std::ptr_fun(&std::tolower<char>), std::locale("")));

    std::cout << a << std::endl;
}