#include <bits/stdc++.h>
using namespace std;
int fact(int x) {
  if (x == 1) return x;
  x = x * fact(x - 1);
  return x;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int t;
  t = 1;
  while (t--) {
    float r, x, y, X, Y, d, length, inter;
    int ans = 0;
    cin >> r >> x >> y >> X >> Y;
    d = 2 * r;
    length = sqrt(pow(Y - y, 2) + pow(X - x, 2));
    if (x == X && y == Y)
      cout << "0";
    else {
      ans = length / d;
      if (modf(length, &inter)) ans++;
      cout << ans;
    }
  }
  return 0;
}
