import time

def concat(n):
	start = time.time()
	s = ""
	for i in range(n):
		s += "Вася" + str(i)
	end = time.time()
	print("%d strings concatenated in %.3f seconds" % (n, end - start))
	
def join(n):
	start = time.time()
	
	def gen(n):
		for i in range(n):
			yield "Вася" + str(i)
			
	s = "".join(gen(n))
	end = time.time()
	print("%d strings joined in %.3f seconds" % (n, end - start))



concat(3000000)
join(3000000)