'use strict';

function main(stdin) {
  const input = stdin.split('\n');
  const N = Number(input.shift());
  const params = input[0].split(' ').map(v => parseInt(v, 10));

  const sorted = params.sort((a, b) => a - b);
  const ans = sorted.reduce((a, b) => (a + b) / 2);
  
  console.log(ans);
}

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