#include <stdio.h>
#include <math.h>

int rad, nsteps;

int read_case() {
  if (scanf("%d %d", &rad, &nsteps) != 2) return 0;
  return rad;
}

void solve_case() {
  double x=0, y=0;
  int i;
  for (i=1;i<=nsteps;i++) {
    if (i%4==1) y = .5*(y +  pow(rad*rad-x*x,.5));
    else if (i%4==2) x = .5*(x + pow(rad*rad-y*y,.5));
    else if (i%4==3) y = .5*(y - pow(rad*rad-x*x,.5));
    else if (i%4==0) x = .5*(x - pow(rad*rad-y*y,.5));
  }
  printf("%.2lf\n",pow(x*x+y*y,.5));
}

main() {
  while (read_case()) solve_case();
}