#include <iostream>
#include <cmath>

int const width = 80;

class screen {
  int cursor; /* for escape-sequence, now not used. */
  double max;
public:
  screen(double max) : cursor(0), max(max) {
    std::cout << std::endl;
  }
  ~screen() { std::cout << std::endl; }
  void out(double x) {
    int cx = (int)(x / max * (width / 2.0) + width / 2.0);
    for (int i = 0; i < cx; i++)
      std::cout << ' ';
    std::cout << 'x' << std::endl;
  }
};

double const k = 0.05;
double const u = 0.18;
double const epsilon = 0.1;

class mass {
  double x, v;
public:
  mass(double x, double v) : x(x), v(v) {}
  void delta() {
    double dv;
    dv = -k * x + ((v < 0.0) ? +1.0 : -1.0 ) * u;
    if (fabs(dv) < epsilon && fabs(v) < epsilon) v = 0.0; else v += dv;
    x += v;
  }
  double position() { return x; }
};

int const Tmax = 200;
double const A = 100.0;
double const v0 = 0.0;
int main() {
  int t;
  screen screen(A);
  mass m(A, v0);
  for (t = 0; t < Tmax; t++) {
    m.delta();
    screen.out(m.position());
  }
  return 0;
}
/* end */