#!/usr/bin/env python3
#  Dan Gau
#  Arrays.py

def main():
	
	#defines sums, and gets number of grades
	numGrades = int(input("How many grades are you entering? "))
	grades = []
	summ = 0
	
	#calcluates sum and gets grades from user.
	#
	for i in range(numGrades):
		grades.append(int(input("Enter the "+ repr(i+1)+ " grade: ")))
		summ = summ + grades[i]
		
	average = summ/numGrades
	
	# Compute the sum of squares of the difference of each term with the average.
	sumSquares = 0
	for i in grades:
		sumSquares = sumSquares + (i - average)**2
	stdev = (sumSquares/numGrades)**.5
	
	# print results
	print("The standard deviation was ",stdev)
	print("The average was ", average)
	i = 1
	for x in grades:
		print("Student ", i, " earned a",getGrade(x,average,stdev))
		i = i + 1
	
	return 0

#returns the letter grade based on grade, average, and standard deviation
def getGrade(gr, ave, std):
	if (gr > ave + std):
		return 'A'
	elif(gr > ave):
		return 'B'
	else:
		return 'C'


if __name__ == '__main__':
	main()