function main(arg) {
	arg = arg.trim().split('\n');
  	var v = arg[1].split(' ').map(str => parseInt(str, 10)).sort((a,b) => a-b),
        n = arg[0], out = 0;
  	out = (v[0]+v[1])/2;
  	for (var i = 2; i < n; i++) {
    	out = (out + v[i])/2
    }
	console.log(out);
}

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