import kotlin.random.Random
fun main() {
    val N = readln().toInt()
    val (A, B) = buildList(N) {
        repeat(N) {
            val (a, b) = readln().split(' ').map { it.toLong() }
            add(Pair(a, b))
        }
    }.unzip()
    var optimalQueries = listOf<Pair<Int, Int>>()
    var minCost = 500_000_000_000_000_000L
    repeat(10000) {
        val copiedA = A.toMutableList()
        val copiedB = B.toMutableList()
        val queries = mutableListOf<Pair<Int, Int>>()
        repeat(50) {
            val u = Random.nextInt(N)
            val v = Random.nextInt(N - 1).let { if (it < u) it else it + 1 }
            queries.add(Pair(u, v))
            copiedA[u] = (copiedA[u] + copiedA[v]) / 2
            copiedA[v] = copiedA[u]
            copiedB[u] = (copiedB[u] + copiedB[v]) / 2
            copiedB[v] = copiedB[u]
        }
        val cost = Math.max(Math.abs(copiedA[0] - 500_000_000_000_000_000L), Math.abs(copiedB[0] - 500_000_000_000_000_000L))
        if (cost < minCost) {
            optimalQueries = queries
            minCost = cost
        }
    }
    println(optimalQueries.size)
    println(optimalQueries.joinToString("\n") { (u, v) -> "${u + 1} ${v + 1}" })
}