First input prompt skipped, while the rest are fine - if-statement

Question

Here's the code in question. When I run the program, if I enter any number of users, the ability to enter the username of the first user is skipped, while I can enter the username of the rest and the code performs as expected.
#include <iostream>
#include <string>
using namespace std;
int main(void)
{
cout << "We would be more than happy to set up an account for you." << endl;
cout << "You may set up to four users, how many would you like to set up?" << endl;
int new_users;
cin >> new_users;
if(new_users < 1 || new_users > 4)
{
cout << "Invalid number, please try again." << endl;
return 0;
}
int user_number = 1;
string user_name_1, user_name_2, user_name_3, user_name_4;
string password_1, password_2, password_3, password_4;
if(new_users == 4)
{
cout << "Please enter the name of user #" << user_number << ": " << endl;
getline (cin, user_name_1, '\n');
cout << "Please enter the password for user: " << user_name_1 << endl;
getline(cin, password_1);
user_number++;
new_users--;
}
if(new_users == 3)
{
cout << "Please enter the name of user #" << user_number << ": " << endl;
getline(cin, user_name_2, '\n');
user_number++;
new_users--;
cout << "Please enter the password for user: " << user_name_2 << endl;
getline(cin, password_2);
}
if(new_users == 2)
{
cout << "Please enter the name of user #" << user_number << ": " << endl;
getline(cin, user_name_3, '\n');
user_number++;
new_users--;
cout << "Please enter the password for user: " << user_name_3 << endl;
getline(cin, password_3);
}
if(new_users == 1)
{
cout << "Please enter the name of user #" << user_number << ": " << endl;
getline(cin, user_name_4, '\n');
user_number++;
new_users--;
cout << "Please enter the password for user: " << user_name_4 << endl;
getline(cin, password_4);
}
cout << "Thank you for setting up an account. Please login." << endl;
cout << "Enter user name: ";
string user, password_attempt;
getline(cin, user);
cout << "Enter password: ";
getline(cin, password_attempt);
if (user == user_name_1 && password_attempt == password_1)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_2 && password_attempt == password_2)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_3 && password_attempt == password_3)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_4 && password_attempt == password_4)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else
{
cout <<"User name or password is invalid, please try again." << endl;
}
cout << "Enter user name: ";
getline(cin, user);
cout << "Enter password: ";
getline(cin, password_attempt);
if (user == user_name_1 && password_attempt == password_1)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_2 && password_attempt == password_2)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_3 && password_attempt == password_3)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else if (user == user_name_4 && password_attempt == password_4)
{
cout << "login successful, welcome user: " << user << endl;
return 0;
}
else
{
cout << "Invalid user. Goodbye." << endl;
return 0;
}
}
/*Things it needs to do
. Take multiple user names
. Set password for each user name
. User able to "login"
. Prompt if user fails to login to login again.
OoO
Ask how many users it would like to set up, up to 4.
Take a user name
set the password for recently taken user name
If the user wishes to exit allow them to; if not repeat, we'll say up to 3 times.
Once all users are entered, they can login.
If the login fails they are offered another attempt.
*/
I've tried a different compiler and it still is showing up. I expected the first user to behave like the rest, not sure what's wrong.