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.
t = int(input())
kg = []
cost = []

for x in range(t):
    a,b = input().split()
    kg.append(int(a))
    cost.append(int(b))

    
day = 0
spend = 0
stor = 0
while day < t :
    if stor >= kg[day] :
        stor -= kg[day]
    else:
        spend += kg[day]*cost[day]
        cheaper = 0
        for y in cost[day+1::]:
            if y > cost[day]:
                cheaper += 1
            else:
                break
        if (cheaper > 0):
            for x in kg[day+1:day+1+cheaper]:
                spend += x*cost[day]
                stor += x
    day += 1
        

print (spend)   
    
        
        
        
        
