Why I can't save and display a sentence when the fragment is placed differently?

Question

Thanks for taking the time of reading my question. So I have this code:

#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])

{
    float pricePerLetter = 0.0;
    string userInput;
    cout << "Welcome" << endl;
    cout << "Please enter sentence: ";
    getline(cin, userInput);
    cout << userInput;      

    cout << "Please enter price per letter: ";
    cin >> pricePerLetter;
    cout << endl;


    system("PAUSE");
    return 0;

}

which runs fine. I am able to save the sentence on userInput and display it. However, when I switch fragments of the code for the one below, the program ends without letting me write the sentence.

#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])

{
    float pricePerLetter = 0.0;
    string userInput;
    cout << "Welcome" << endl;
    cout << "Please enter price per letter: ";
    cin >> pricePerLetter;
    cout << endl;

    cout << "Please enter sentence: ";
    getline(cin, userInput);
    cout << userInput;

    system("PAUSE");
    return 0;

}

I don't get why this occurs.