Duff is addicted to meat! Malek wants to keep her happy for *n* days. In order to be happy in *i*-th day, she needs to eat exactly *a*<sub class="lower-index">*i*</sub> kilograms of meat.

There is a big shop uptown and Malek wants to buy meat for her from there. In *i*-th day, they sell meat for *p*<sub class="lower-index">*i*</sub> dollars per kilogram. Malek knows all numbers *a*<sub class="lower-index">1</sub>, ..., *a*<sub class="lower-index">*n*</sub> and *p*<sub class="lower-index">1</sub>, ..., *p*<sub class="lower-index">*n*</sub>. In each day, he can buy arbitrary amount of meat, also he can keep some meat he has for the future.

Malek is a little tired from cooking meat, so he asked for your help. Help him to minimize the total money he spends to keep Duff happy for *n* days.
The first line of input contains integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">5</sup>), the number of days.

In the next *n* lines, *i*-th line contains two integers *a*<sub class="lower-index">*i*</sub> and *p*<sub class="lower-index">*i*</sub> (1 ≤ *a*<sub class="lower-index">*i*</sub>, *p*<sub class="lower-index">*i*</sub> ≤ 100), the amount of meat Duff needs and the cost of meat in that day.
count = int(input())
every =[]
price = []
meat = []
final = 0
for i in range(count):
    every.append(list(map(int, input().split())))
for i in range(count):
    price.append(every[i][1])
for i in range(count):
    meat.append(every[i][0])
price.sort()
def deletion(start, massive):
    fin = []
    for i in range(start):
        fin.append(massive[i])
    return fin
def sum(massive):
    fin = 0
    for i in range(len(massive)):
        fin += massive[i][0]*massive[0][1]
    return fin
def antideltion(massive1, massive2):
    fin = []
    for i in range(len(massive1)):
        if massive1[i] not in massive2:
            fin.append(massive1[i])
    return fin
for a in range(count):
    for i in range(count):
        try:
            if every[i][1] == price[a]:
                final += sum(antideltion(every, deletion(i, every)))
                every = deletion(i, every)
        except:
            break
print(final)