#include <iostream>
#include <algorithm>
#include <ctype.h>
using namespace std;

string lower_case(string& x)
{
    std::transform(x.begin(), x.end(), x.begin(), ::tolower);

    return x;
}

int main()
{
 string str = "HELLO WORLD";
 lower_case(str);
 
 cout << str;

 return 0;
}