process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = [];
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});

reader.on('line', (line) => {
  lines.push(line);
});

reader.on('close', () => {
  var N = Number(lines[0]);
  var vary = lines[1].split(' ');
  console.log(vary)
  while (vary.length > 1){
    vary.sort(function(a,b) {
      if (a<b) {
        return -1;
      }
      if (a>b) {
        return 1;
      }
      return 0;
    });
    vary.push((Number(vary[0])+Number(vary[1]))/2.0);
    vary.splice(0,2)
  }
  console.log(vary[0])

});
