#include <bits/stdc++.h>
using namespace std;
long long a = 0, b = 0, c = 0, d = 0, e = 0, f = 0, mx = 0, ans = 0;
int main() {
  long long t;
  a = 0;
  b = 0;
  c = 0;
  d = 0;
  e = 1;
  ans = 0;
  mx = 0;
  cin >> a >> b >> c >> d >> e;
  a = 2 * a;
  long long x, y;
  x = abs(b - d);
  y = abs(c - e);
  x = x * x;
  y = y * y;
  x = x + y;
  double X = sqrt(x);
  ans = X / a;
  if (ans < X / a) ans++;
  cout << ans << endl;
}
