day = input()

if day == 'Monday' or day == 'Tuesday' or day == 'Wednesday' or day == 'Thursday' or day == 'Friday':
    print('Working day')
elif day == 'Saturday' or day == 'Sunday':
    print('Weekend')
else:
    print('Error')

Или така:

day = input()

if day in ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'):
    print('Working day')
elif day in ('Saturday', 'Sunday'):
    print('Weekend')
else:
    print('Error')

Решение с тернарен оператор:

day = input()

print('Working day' if day in ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday')
      else 'Weekend' if day in ('Saturday', 'Sunday') else 'Error')

Решение с масив:

day = input()

working_day = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday']
weekend = ['Saturday', 'Sunday']

print('Working day' if working_day.__contains__(day) else 'Weekend' if weekend.__contains__(day) else 'Error')