from collections import defaultdict

time_dict = defaultdict(int)
penalty = 0

for _ in range(11):
    T, V = map(int, input().split())
    penalty += 20*V
    time_dict[T] += 1

time = 0
time_dict_sorted = dict(sorted(time_dict.items(), key=lambda x: x[0]))
while time_dict_sorted:
    keys = list(time_dict_sorted.keys())

    time += keys[0]
    time_dict_sorted[keys[0]] -= 1
    penalty += time
    if time_dict_sorted[keys[0]] == 0:
        del(time_dict_sorted[keys[0]])
print(penalty)