#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, a, b;
  cin >> r >> x >> y >> a >> b;
  int d = 2 * r;
  long double len = sqrt((x - a) * (x - a) + (y - b) * (y - b));
  int flag;
  if ((len - floor(len)) == 0)
    flag = 1;
  else
    flag = 2;
  int ans;
  if (flag == 1) {
    int length = len;
    if (length % d == 0)
      ans = length / d;
    else
      ans = (length / d) + 1;
  } else if (flag == 2) {
    int length = floor(len);
    ans = (length / d) + 1;
  }
  cout << ans;
  return 0;
}
