# -*- coding:utf-8 -*-
import math

if __name__ == "__main__":
	n = input()
	ans = 0
	for i in xrange(n):
		c,d = map(int,raw_input().split())
		ans += (c+1) / 2 * d
		ans = math.fmod(ans,10**9+7)
	print int(ans)