#include <bits/stdc++.h>
using namespace std;
double dist(long x, long y, long x1, long y1) {
  double ans = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  ans = sqrt(ans);
  return ans;
}
int main() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
  int r;
  long x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  double d = dist(x, y, x1, y1);
  int cnt = 0;
  while (d > 2 * r) {
    d = d - 2 * r;
    cnt += 1;
  }
  if (d > 0) {
    cnt += 1;
  }
  cout << cnt;
}
