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.
l = []
for _ in range(int(input())):
    t = list(map(int, input().split()))
    l.append(t)
p,q,sum = 0,1,0
inif = False
inelseif = False
if len(l) == 1:
    print(l[0][0]*l[0][1])
else:
    while q <= len(l):
        if (q == len(l)) and (inif == True):
            sum += l[p][0] * l[p][1]
            q += 1
        elif (q == len(l)) and (inelseif == True):
            sum += l[p][1]*l[p][0]
            q += 1
        else:
            if l[p][1] > l[q][1]:
                sum += l[p][0]*l[p][1]
                p = q
                q += 1
                inif = True
                inelseif = False
            else:
                sum += (l[q][0]*l[p][1])
                q += 1
                inif = False
                inelseif = True
    print(sum)