N = int(input())

sum = 0
for x in range(N):
    l = input()
    l = l.split(" ")
    l = [int(x) for x in l]

    if l[0] % 2 == 0:
        sum = (sum + l[0] / 2 * l[1]) % (10 ** 9 + 7)
    else:
        sum = (sum + (l[0] + 1) / 2 * l[1]) % (10 ** 9 + 7)

print(str(int(sum)))