main = input => {
  input = input.split('\n');
  var v = input[1].split(' ').map(parseFloat);
  
  for(var i = 0;v.length !== 1;i++){
    v.sort((a,b) => a < b);
    var num1 = v.pop();
    var num2 = v.pop();
    v.push((num1 + num2)/2);
  }
  console.log(v[0])
}
main(require('fs').readFileSync('/dev/stdin','utf8'));