n = int(input())
total = 0

for i in range(n):
  c, m = map(int, input().split())
  if c <= 2:
    total += m
  elif c % 2 == 0:
    total += (c - 2) * m
  else:
    total += (c - 1) * m

print(total%(10**9 + 7))