---

# Решение задания

def add_student(student_name, student_age):
    try:
        age = int(student_age)
    except ValueError:
        print('Student age must be an integer')
        return

    try:
        if age < 0:
            raise ValueError('Student age cannot be negative')
        if age == 0:
            raise ValueError('Student age cannot be zero')
        if age < 10:
            raise ValueError('Student age must be at least 10')
        if age > 150:
            raise ValueError('Student age cannot be greater than 150')

        if len(student_name) < 5:
            raise ValueError('Student name must contain at least five characters')
        if len(student_name) > 20:
            raise ValueError('Student name cannot be longer than 20 characters')
        if not student_name.isalpha():
            raise ValueError('Student name must contain only letters')
    except ValueError as err:
        print(err)
        return

    students.append({
        'name': student_name,
        'age': age,
        'marks': []
    })
    print(f'New student #{len(students) - 1} added')