C++ :: Having Struct As A Key For A Map

So why does this not work? As an example:

struct example {
int x; int y;
};
int main() {
example variable;
variable.x = 1;
variable.y = 2;
map<example, int> something;
something[variable] = 3;
return 0;
}

And I get a very long error message from the compiler. I tried using an enum as the key as well and that worked just fine, but I guess that's just the same as having an integer as the key. But anyway, what's the problem with this? Is there any way to make it work?