def validateInput(prompt, lowBound, highBound):
    validData = False
    while not validData:
        number = input(prompt)
        if number.isdigit():
            number = int(number)
            if number >= lowBound and number <= highBound:
                validData = True
            else:
                print("Input invalid. Please try again")
        else:
            print("Input invalid. Please try again")
    return number

grades = []
numGrades = validateInput("Enter number of grades: ", 1, 999)

for count in range(1, numGrades+1):
    grade = validateInput(f"Enter grade {count}: ", 0, 100)
    grades.append(grade)

low = min(grades)
high = max(grades)
average = sum(grades) / numGrades

print(grades)