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.
minPrice,s,pq,arr = 101,0,[],[]
for _ in range(int(input())):
    
    quantity,price = map(int, input().split())
    pq.append((quantity,price))
    minPrice = min(price, minPrice)
    
    s += quantity
    
    arr.append(s)
ans = 0
for i,j in enumerate(pq):
    
    if j[1] == minPrice:
        if i-1 >= 0:
            ans += (minPrice * (arr[-1] - arr[i-1]))
        else:
            ans += (minPrice * arr[-1])
        break
    else:
        ans += (j[1]*j[0])
print(ans)