Overloading << operator ostream [closed]

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Why doesn't the line below work?

#include <iostream>

std::ostream& operator <<( std::ostream& os, const char *c)
{
    os << c; // why does this line doesn't work?
    return os;
}

int main()
{
    const char *c = "Hi";
    std::cout << c;
}

---

The problem is std::ostream& operator <<( std::ostream& os, const char *c) has already been overloaded in iostream.