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.
from sys import stdin

def read_lines(sep=' ', input_type=None):
    #list of rows
    _lines = stdin.readlines()
    cast = input_type is not None
    lines = []
    for line in _lines:
        line = line[:-1].split(sep)
        if cast:
            line = [input_type(x) for x in line]
        lines.append(line)
    return lines


MAXINT=2**63-1
if __name__ == '__main__':

    lines = read_lines(input_type=int)
    
    t = lines[0]
    lines = lines[1:]

    runmin_p = MAXINT
    cost = 0
    for line in lines:
        a,p = line
        if p < runmin_p:
            runmin_p=p
        
        cost += a*runmin_p
    print(cost)