main = input => {
  input = input.split('\n');
  var v = input[1].split(' ').map(parseFloat);
  
  var result = v.sort((a,b) => a - b).reduce((acc,cur) =>(acc + cur)/2);
  console.log(result);
}
 
/*  var input = `2
 3 4`;
main(input);
 */  
Main(require("fs").readFileSync("/dev/stdin", "utf8")); */