"use strict";
main(require("fs").readFileSync("/dev/stdin", "utf8").replace(/\r?\n$/, "").split(/\r?\n/));

function main(lines){
	while(lines.shift() != "0"){
		var list = lines.shift().split(" ").map(Number);
		var ave = list.reduce(function(a,b){return a+b;}) / list.length;
		console.log(Math.sqrt(list.map(function(s){return Math.pow(s-ave,2)}).reduce(function(a,b){return a+b})/list.length));
	}
}