'use strict';
function main(input) {
  const args = input.split('\n'),
        N = parseInt(args[0]),
        D = args[1].split(' ');
  for (let i = 0; i < N; ++i) {
    D[i] = parseDouble(D[i]);
  }
  D.sort();
  let value = D[0];
  for (let i = 1; i < N; ++i) {
    value = (value + D[i]) /2;
  }
  console.log(value);
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));
