#include <bits/stdc++.h>
int main() {
  float e, c, a, b, r, x, y, x1, y1, d, i;
  int z;
  scanf("%f %f %f %f %f", &r, &x, &y, &x1, &y1);
  a = x1 - x;
  a = a * a;
  b = y1 - y;
  b = b * b;
  c = a + b;
  c = pow(c, 0.5);
  d = r * 2;
  e = c / d;
  z = e + 1;
  printf("%d", z);
  return 0;
}
