import strutils, sequtils, math

proc trfm(x: int): int = x mod (10 ^ 9 + 7)

let N = stdin.readLine.parseInt
var C, D, cnt: int

for i in 0 ..< N:
  (C, D) = stdin.readLine.split.map parseInt
  if C mod 2 == 0: C = C div 2 else: C = C div 2 + 1
  cnt += C.trfm * D.trfm
  cnt = cnt.trfm

echo cnt