const main = (N,U) => {
    const result = U.sort((a,b) => a - b).slice(1).reduce((x,i) => {
        return x = (x + i)/2
    },U[0])
    return result
}

const input = require('fs').readFileSync('/dev/stdin','utf8').split("\n")
const N = Number(input[0])
const U = input[1].split(" ").map( x => Number(x))
console.log(main(N,U))