std cin input with spaces

Question

#include <string>

std::string input;
std::cin >> input;

The user want to type "Hello World." 

However, cin fails to recognise the space between the two words. 

How do I get Cin to see the entire Hello World?

I'm trying this using structs, and cin.getline doesn't appear to work. 

This is my code:

struct cd

{
    std::string CDTitle[50];
    std::string Artist[50];
    int number_of_songs[50];
};

std::cin.getline(library.number_of_songs[libNumber], 250);

This yields an error. Any ideas?