def F1(x) : 
	retour=x*x 
	return retour

a = float(input("a : ")) 
b = float(input("b : ")) 
nbtrapezes = float(input("nbtrapezes : ")) 
if (nbtrapezes>0 and b>a) : 
	approxintegrale=0 
	pas=(b-a)/nbtrapezes 
	for i in range(0, nbtrapezes) :
		approxintegrale=approxintegrale+pas/2*(F1(a+i*pas)+F1(a+(i+1)*pas)) 
	print "approxintegrale : ", approxintegrale