function main(input){
    let lines = input.split("\n");
    let count = parseInt(lines.shift());
        while(count!==0){
//            console.log(lines.shift())
        let nums = allint((lines.shift()).split(" "));
        let sum = getSum(nums);
        let avg = sum/nums.length;
        let answer = 0;
        for(let i=0;i<nums.length;i++){
            answer += Math.pow(nums[i]-avg,2)/nums.length;
        }
        console.log(Math.sqrt(answer));
        
        count = parseInt(lines.shift());

    }
    
    
}
function allint(arr){
    return arr.map(x=>parseInt(x));
}
function getSum(arr){
    return arr.reduce((sum,x)=>sum+=x);
}
main(require("fs").readFileSync("/dev/stdin","utf-8"));
