#試験監督(1)

N = int(input())
sum = 0
m = 10 ** 9 + 7

for i in range(N):
    cd = list(map(int , input().split()))
    cd[0] = ((cd[0] + 1) // 2) % m
    cd[1] %= m
    sum += cd[0] * cd[1]
    sum %= 10 ** 9 + 1

print(sum)