Help on If, else if, else statements

 

 /*
Description: this program will ask the user to input the number of a month then 
 tell the user how many days are in that month
 
 Algorithm
 1. Months 1,3,5,7,8,10,12 have 31 days 
 2. Month  2 has 28 or 29 days
 3. Months 4,6,9,11 have 30
 4. Any number above 12 is not valid
 */

#include <iostream>
using namespace std;
int main()
{
   
    int y;
    cout << "Input The Number of The Month: ";
    cin >> y;
    if ( cin.fail())
    {  cout << "Input Error Please Enter A number!"<<"\n";
        return 1;
    }
    
    if ( y >= 13)
    {  cout << "Please Enter a valid Number of a month "<<"\n";
        return 2;
    }
    
    if ( y == 1 || 3 || 5 || 7 || 8 || 10 || 12 )
    
    cout << y << " Has 31 days" << endl ;
        
    
    
    else if (y ==  2 ) 
    
     cout << y << "Has 28 days in a regular year 29 days in a leap year" << endl ;
    
     
    
     else if( y == 4 || 6 || 9 || 11 )
    
     cout << y << "Has 30 days" << endl ;
              
     
    
    
 return 0;
}