Please help

I am very new to python and I am trying to build a code that allows a student to input their grades from 3 assignments (or 2 assignments and one midterm) and see what grade they would need on the final exam in order to reach their desired final grade for the entire class. Assignment 1 is out of 5, assignment 2 is out of 15 and the midterm is out of 35, which leaves the final exam out of 45. I also have to write a boundary for each mark they got once they input it into the shell, for example the mark for assignment 1 can only fall between 0 and 5 so I need some sort of popup that alerts them they input a wrong value.

ANY HELP greatly appreciated!!!

desiredmark = int(input("Enter your desired grade: "))
midterm = int(input("Enter your score for the midterm (out of 35): "))
assignment1 = int(input("Enter your score for assignment 1 (out of 5): "))
assignment2 = int(input("Enter your score for assignment 2 (out of 15): "))
exam = (midterm + assignment1 + assignment2 + 45)/100
if exam >49:
    print("Your desired grade is not possible with your current grades")
elif desiredmark <50:
    print("You have already surpassed your desired goal of: " , desiredmark)

You’ve said what you need to do, but not what is stopping you, there are no questions here