Optimizing simple C++ grading program

I have started working on the projects listed here. I want to practice my C++ coding skills. I would love any constructive criticism I can get!

This is for the very first problem, #1 "Grading Program"

#include 
using std::cout;
using std::cin;

int main()
{
    int UserNumber;
    char Grade;

    cout > UserNumber;
    cout  89 && UserNumber  79 && UserNumber  69 && UserNumber  59 && UserNumber  -1 && UserNumber < 61)
    {
        Grade = 'F';
    }
    else
    {
        Grade = 'Z';
    }

    switch (Grade)
    {
    case 'A':
        cout << "Perfect! You got a: " << Grade;
        break;
    case 'B':
        cout << "Could've been worse. You got a: " << Grade;
        break;
    case 'C':
        cout << "It's okay I guess, you got a: " << Grade;
        break;
    case 'D':
        cout << "Uggh.. You got a: " << Grade;
        break;
    case 'F':
        cout << "Better luck next time! You got a: " << Grade;
        break;
    case 'Z':
        cout << "Undefined value! Make sure it's a value from 0-100!";
        break;

    }
    cout << "\n\n\n\t\t\t";
    return 0;
}

There's probably much that can be done, but I'll give it a quick review:

-
Are only integer grades allowed? They can be decimals in real life, and that would make for a more robust grading system.

-
Consider renaming UserNumber to something like numericalGrade. The former sounds like it's for an ID number, not a grade.

-
Do not "list" variables at the top of a function in C++, unless it's absolutely necessary. Here, you can declare UserNumber between the std::cout and std::cin.

-
There's no need for a Z case here. Use a default case instead, which will be reached if no other case is reached.

-
You don't need an explicit return 0 at the end. The compiler will do this return for you at the end of main() as successful termination is always implied here.

StackExchange Code Review Q#67276, answer score: 5