const MOD = 1_0000_0000_7
const HIGH = int32.high
proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    var k = getchar_unlocked()
    if k < '0' or k > '9': break
    else: result = 10 * result + k.ord - '0'.ord

proc scanf(formatstr: cstring){.header: "<stdio.h>", varargs.}
var n:int
scanf("%ld\n",addr n)
var res = 0
for _ in 0..<n:
  var c = scan()
  var d = scan()
  # scanf("%lld %lld\n",addr c,addr d)
  c = (c+1) shr 1
  if c > HIGH : c = c mod MOD
  if d > HIGH : d = d mod MOD
  res += c * d
  if res > HIGH: res = res mod MOD
echo res