
function Main(input) {
  input = input.split("\n");	
  var input1 = input[1].split(" ");	
  input1 = input1.map(e=>{
    return parseInt(e,10);
  })
  
  input1.sort((a,b)=>{
    return a-b;
  })
  var result=input1.reduce((prev,curr)=>{
    return (prev+curr)/2
  });
  console.log(result)
  
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));