fun main(arr:Array<String>) {
    val deskKind = readLine()!!.toInt()
    val mod = 1000000000 + 7
    var total = 0L
    for(i in (0 until  deskKind)) {
        val (isu, tsukue) = readLine()!!.split(" ").map { it.toLong() }
        var tmp = isu / 2
        if (isu % 2 != 0L) {
            tmp++
        }
        tmp = tmp % mod
        tmp = tmp * (tsukue % mod)
        tmp = tmp % mod
        total += tmp
        total = total % mod
    }
    println(total)
}