1 #include <iostream>
   2 #include <cmath>
   3 
   4 int main()
   5 {
   6     double x, n(0), sum(0), sqr(0);
   7     while (std::cin >> x) {
   8         ++n;
   9         sum += x;
  10         sqr += x * x;
  11     }
  12     register const double xbar(sum / n);
  13     std::cout.precision(12);
  14         std::cout
  15         << n << "\n"
  16         << xbar << "\n"
  17         << std::sqrt(sqr / n - xbar * xbar)
  18         << std::endl;
  19 }