A program that collects a series of grades $($ranging $0100)$ until the user indicates that they don$$t want to continue entering values using a sentinel value. $-1$ is a good choice for a sentinel here.$)$

The program should display the average of the grades entered. Tell the user to $$Enter a value from $0-100$ or $-1$ to quit.$$ Tell them this in the loop until they enter $-1.$ Once they enter, will need a output statement outside of the loop to tell them what the average grade was. Write in pseudocode