var input = ""
process.stdin.resume();
process.stdin.setEncoding('utf-8');
process.stdin.on('data', function(chunk) {
  input += chunk;
});
 
process.stdin.on('end', function() {
  input = input.split("\n");

  var i = 0;
  while (input[i] != 0) {
    i++;
    s = input[i++].split(" ")
    
    var sum = 0;
    for (j = 0; j < s.length; j++) {
      sum += parseInt(s[j], 10);
    }
    average = sum / s.length;

    var x = 0;
    for (j = 0; j < s.length; j++) {
      x += Math.pow((s[j] - average), 2);
    }
    console.log(Math.sqrt(x / s.length));
  }
});