import math

N = int(input())
C = [input() for n in range(N)]

total = 0
mod = 10 ** 9 + 7

for i in range(N):
    c = C[i].split()
    cheer_num = ((int(c[0]) + 1) // 2)
    desk_num = cheer_num * int(c[1])
    total += desk_num
print(total % mod)