function main (input) {
	input = input.trim().split('\n');
  	const n = Number(input[0]);
  	const vs = input[1].split(' ').map(n => Number(n));
  	vs.sort();
  	let result = (vs[0] + vs[1])/2;
  	for (let i = 2; i < vs.length; i++) {
      const v = vs[i];
      result = (result + v)/2;
    }
  	console.log(result);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));