#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
bool sortinrev(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.first > b.first);
}
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second < b.second);
}
long long int power(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  double x1, x2, y1, y2, r;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double d = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
  double a = d / (2 * r);
  int b;
  if ((int)a * 2 * r == d)
    b = 0;
  else
    b = 1;
  if (b == 0)
    cout << (int)a;
  else
    cout << (int)a + 1;
  return 0;
}
