import kotlin.math.sqrt

fun main() {
    val k = readInt()
    val pts = List(k) { readInts() }
    println(pts.minOf {(x0, y0) ->
        pts.sumOf { (x1, y1) -> sqrt((x1 - x0) * 1.0 * (x1 - x0) + (y1 - y0) * 1.0 * (y1 - y0)) }
    } / (k - 1))
}

private fun readInt() = readln().toInt()
private fun readLongs() = readStrings().map { it.toLong() }
private fun readStrings() = readln().split(" ")
private fun readInts() = readStrings().map { it.toInt() }