N = int(raw_input())
countSum = 0
for i in xrange(N):
	C,D = map(long,raw_input().split())
	C,D = C % (1000000000 + 7) ,D % (1000000000 + 7)
	if C % 2 == 0:
		countSum += (C * D) / 2
	else:
		countSum += ((C - 1) * D)
print countSum % (1000000000 + 7)