C++ 20 , How to represent Universal character names \unnnn such as the EuroSign in R String?

C++ 20 , How to represent Universal character names \unnnn such as the EuroSign in R String? The Following code failed to represent the character despite the Synatx is Correct?

#include <iostream>

using namespace std;

int main()
{
    cout << R"(12.5 \u20AC)";
    return 0;
}