#!/usr/bin/env python3

N = int(input())
num = 0
mod = ((10 ** 9) + 7)
for i in range(N):
    C, D = [int(x) for x in input().split()]
    num += int((int(C / 2) % mod) * D)
    if C % 2 == 1:
        num += D

num = num % mod
print(int(num))