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 functools import reduce
import sys, os
import math
from collections import Counter

TC = False

class Meat():
    def __init__(self) -> None:
        self.day = 0
        self.price = 0


def solve():
    N = int(input())
    meats = [Meat() for _ in range(N)]
    for i in range(N):
        meats[i].day, meats[i].price = map(int, input().split())
    
    price = meats[0].day*meats[0].price
    x = meats[0].price

    for i in range(1, N):
        if meats[i].price < x:
            price += meats[i].day*meats[i].price
            x = meats[i].price
        else:
            price += meats[i].day*x
        
    print(price)
    

if os.path.exists('input.txt'):
    debug = True
    sys.stdin = open("input.txt","r")
    #sys.stdout = open("output.txt","w")

if TC:
    for _ in range(int(input())):
        solve()
else:
    solve()