N = int(input())
n = 10**9 + 7
L = []
for i in range(N):
    c,d = map(int,input().split())
    L.append([c,d])
sum = 0
for i in range(N):
    l0 = L[i][0] * L[i][1]
    l1 = (L[i][0] + 1) * L[i][1]
    if L[i][0] % 2 == 0:
        sum += int(l0/2)
    else:
        sum += int(l1/2)
    sum %= n
print(sum)