Meme

num = int(input())
dic = []

for x in range(num):
	m, s = input().split(' ')
	dic.append(s)

for x in range(len(dic)):
	dic[x] = int(dic[x])

dic = sorted(dic, reverse = True)
count = 0

for x in range(num-5):
	warn_num = 0
	while dic[x+warn_num] != 0:
		for y in range(6):
			dic[x+y] -= 1
			if dic[x+y] == 0:
				warn_num = y
		count += 1
	dic[x+warn_num] = dic[x+5]

print(count*5)