The anwser for Decision Statements - Excercise 2 is

var = int(input('Enter the mark :'))
if var > 90 and var <= 100:
grade = 'S'
elif var >= 80 and var < 90:
grade = 'A'
elif var >= 70 and var < 80:
grade = 'B'
elif var >= 60 and var < 70:
grade = 'C'
elif var >= 50 and var < 60:
grade = 'D'
elif var >= 40 and var < 50:
grade = 'E'
elif var < 40:
grade = 'F'
print('You have scored %s grade' %grade)