function main(arg) {
	arg = arg.trim().split('\n');
  	var v = arg[1].split(' ').map(str => parseInt(str, 10)),
        n = arg[0],
        out = 0;
    v = v.sort(function(a, b) {
      return a - b
    });
    out = (v[0] + v[1])/2
  	if (n-1 === 1) {
    	console.log(out);
    } else{
      for (var i = 2; i < n; i++) {
        out += v[i];
        out /= 2;
      }
      console.log(out);
    }
}

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