import std.algorithm;
import std.array;
import std.conv;
import std.math;
import std.range;
import std.stdio;
import std.string;
import std.typecons;

T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;

void main() {
    while (true) {
        int n = readint;
        if (n == 0) break;

        auto ss = readints;
        double avg = 1.0 * ss.sum / n;
        auto a2 = ss.map!(e => (e - avg) ^^ 2).sum / n;
        writefln("%.6f", sqrt(a2));
    }
}

