'use strict'

const main = input => {
	const args = input.split('\n').map(arg => arg.split(' '))
	const N = parseInt(args[0][0], 10)
	let v	= args[1].map(arg => parseInt(arg, 10)).sort((a, b) => a - b)

	while (v.length > 1) {
		const t1 = v.shift()
		const t2 = v.shift()
		v.push((t1 + t2) / 2)
		v = v.sort((a, b) => a - b)
	}

	console.log(v[0])
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'))
