N = int(input())
L = [list(map(int, input().split())) for x in range(N)]
s = 0

for n in range(N):
    if L[n][0] % 2 == 0:
        s += L[n][0]*L[n][1]/2
    else:
        s += (L[n][0]+1)*L[n][1]/2

print(int(s) % 1000000007)