function Main(input) {
  const inputs = input.split("\n");
  const n = parseInt(inputs[0], 10);
  var nums = new Array(n)
  nums = inputs[1].split(" ");
  const result = nums.map(num => parseInt(num, 10))
    .sort((a, b) => a - b)
    .reduce((acc, value) => (acc + value) / 2);
  console.log(result);
}
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));