#include <bits/stdc++.h>
using namespace std;
struct node {
  int x, num;
} a[100];
bool cmp(node a, node b) { return a.x < b.x; }
void process() {
  int r, x, y, fx, fy, res = 0;
  cin >> r >> x >> y >> fx >> fy;
  double d = sqrt((x - fx) * (x - fx) + (y - fy) * (y - fy));
  while (d > 0) {
    d -= 2 * r;
    res++;
  }
  cout << res << endl;
}
int main() {
  int T = 1;
  while (T--) {
    process();
  }
  return 0;
}
