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
  cnt += (C.float / 2.0).ceil.int.trfm * D.trfm
  cnt = cnt.trfm

echo cnt