C++ :: Finding A String Within Array?

i just want to check to see if one word (string) or one sentance is equal to any others within an array. My code

so basically i want to check if a is equal to either "sleep", "in", or "bed". Or even if the string within a is equal to "sleep in bed" as one string.

I have used the following but even if i get it correct and it says correct it says incorrect another 2 times because it is saying yeah you have gotten one right out of the possible 3. Even if I type "sleep in bed" it still does it (prints out incorrect another 2 times. Also are there any good books to start off with c++?

string a;
string aa[3] = {"sleep", "in", "bed"};
for(int i = 0; i < 3; i++) {
if(a == aa[i]) {
cout << "CORRECT!" << endl;
} else {
cout << "INCORRECT!" << endl;
}
}