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.
x=int(input())
t=0
p=[]
q=[]
for n in range(x):
 if n!=x-1:   
    a,b=map(int,input().split())
    q.append(a)
    if len(p)==0:
        p.append(b)
    else:
        if b>=p[len(p)-1]:
            p=p
        else:
            q=q[0:len(q)-1]
            aa=sum(q)
            t=t+aa*p[0]
            q=[]
            q.append(a)
            p=[]
            p.append(b)
 else:
    
     a,b=map(int,input().split())
     if b>=p[len(p)-1]: 
         q.append(a)
         p.append(b)
         p.sort()
         aa=sum(q)
         t=t+aa*p[0]
     else:
         aa=sum(q)
         t=t+p[0]*aa
         q=[]
         p=[]
         q.append(a)
         p.append(b)
         t=t+q[len(q)-1]*p[len(p)-1]
       
print(t)     
     
    
