'use strict'
Object.defineProperty(exports, '__esModule', { value: true })
exports.main = (_N, dList) => {
  const sortedDList = [...dList].sort()
  if (sortedDList.length % 2 !== 0) return 0
  const half = sortedDList.length / 2
  return sortedDList[half] - sortedDList[half - 1]
}
const exec = () => {
  const input = require('fs').readFileSync('/dev/stdin', 'UTF-8')
  const [N, D] = input.split('\n')
  const dList = D.split(' ').map(d => Number(d))
  const res = exports.main(Number(N), dList)
  console.log(res)
}
console.log(2)
