If you have aim please aim me, please!

I have the following code but it spits out all the months at one time I just want one month. How do i fix my code!

//Mid Term Assignment
//3/11/02
//Rob Gross
//CS170

#include <iostream>
using std::cout;
using std::cin;
using std::endl;

void main()

{
int month;
int January = 31;
int February = 28;
int March = 31;
int April = 30;
int May = 31;
int June = 30;
int July = 31;
int August = 31;
int September = 30;
int October = 31;
int November = 30;
int December = 31;

std::cout << "This program will calculate how many days there are between two given years! \n\n";
std::cout << "Enter your Favorite month? "; // prompt
std::cin >> month;
std::cout << "January has " << January << " days" << endl;
std::cout << "February has " << February << " days" << endl;
std::cout << "March has " << March << " days" << endl;
std::cout << "April has " << April << " days" << endl;
std::cout << "May has " << May << " days" << endl;
std::cout << "June has " << June << " days" << endl;
std::cout << "July has " << July << " days" << endl;
std::cout << "August has " << August << " days" << endl;
std::cout << "September has " << September << " days" << endl;
std::cout << "October has " << October << " days" << endl;
std::cout << "November has " << November << " days" << endl;
std::cout << "December has " << December << " days" << endl;