#include <bits/stdc++.h>
using namespace std;
void start() {}
vector<long int> g[200007];
map<long int, bool> vis;
long int siz = 0;
void dfs(long int x) {
  vis[x] = 1;
  siz++;
  for (auto i : g[x]) {
    if (!vis[i]) {
      dfs(i);
    }
  }
  return;
}
double dist(long int x, long int y, long int a, long int b) {
  double ans = sqrt((a - x) * (a - x) + (b - y) * (b - y));
  return ans;
}
void sober() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double ans = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  ans = ans / (2 * r);
  cout << ceil(ans) << "\n";
}
signed main() {
  start();
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long int t = 1;
  while (t--) {
    sober();
  }
}
