from os import initgroups
from sys import stdin
from collections import *
from heapq import *
from random import *
input = lambda: stdin.readline().strip()
# read1 = stdin.read().split()
# idx = 1

mod1 = 2**64
f = defaultdict(int)
ans = 0
for i in range(1,int(input())+1):
    x,y = map(int,input().split())
    ans += i*f[x]
    f[x] = y
    ans %= mod1
print(ans)