process.stdin.resume();
process.stdin.setEncoding("utf8");

const reader = require("readline").createInterface({
  input: process.stdin,
  output: process.stdout,
});

const lines = [];

reader.on("line", (line) => {
  lines.push(line);
});

reader.on("close", () => {
  let i = 0;
  while (true) {
    const n = lines[i++] - 0;
    if (!n) break;
    const nn = lines[i++].split(" ").map(Number);
    const av = nn.reduce((a, b) => a + b, 0) / n;
    console.log(
      Math.sqrt(nn.reduce((p, c) => p + Math.pow(c - av, 2), 0) / n).toFixed(5)
    );
  }
});

