function compareFunc(a, b) {
    return a > b;
}
function Main(input) {
  input = input.trim()
  input = input.split("\n");
  var N = input[0]
  var V = input[1].split(" ").map(Number);
  V.sort(compareFunc)
  for(var i=0;i<V.length-1;i++){
    V[i+1] = (V[i]+V[i+1])/2
  }
  console.log(V[V.length-1])
}Main(require("fs").readFileSync("/dev/stdin", "utf8"));