'use strict'
function main(input: string) {
    const n: number = Number(input.split('\n')[0]);
    const u: number[] = input.split('\n')[1].split(' ').map(Number).sort();
    const r = u.reduce((acc, cur) => (acc + cur) / 2);
    console.log(r);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));