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.

def main():
    days = int(input())

    need_per_day = []
    price_per_day = []
    for _ in range(days):
        i = input()
        i_splitted = i.split(' ')
        need_per_day.append(int(i_splitted[0]))
        price_per_day.append(int(i_splitted[1]))

    print(get_minimal_money(need_per_day, price_per_day))

def get_minimal_money(need_per_day, price_per_day):
    total = 0
    curr_min = 999999
    for i in range(len(need_per_day)):
        if price_per_day[i] < curr_min:
            curr_min = price_per_day[i]
        total += need_per_day[i] * curr_min
    return total

if __name__ == "__main__":
    main()