#write a function average that has three parameters and return average of 
#parameters

#write a program that reads grades in three courses for 2 students
#and finds average grade for each student.

#write a function that checks validity of the input
#is_valid has three parameters, and returns True is parameters are valid 
#and False otherwise

def average(a,b,c):

	return (a+b+c)/3

def is_valid(a,b,c):
	value1=((a>=0) and (a<=100))
	value2=((b>=0) and (b<=100))
	value3=((c>=0) and (c<=100))
	if(value1 and value2 and value3):
		return True
	else:
		return False	

def main():
	counter=1
	print("student #", counter)

	g1=int(input("grade 1 "))
	g2=int(input("grade 2 "))
	g3=int(input("grade 3 "))
	print("average grade for student", counter, "is", average(g1,g2,g3))
	
	counter=counter+1
	g1=int(input("grade 1 "))
	g2=int(input("grade 2 "))
	g3=int(input("grade 3 "))

	print("average grade for student", counter, "is", average(g1,g2,g3))
main()