#include <bits/stdc++.h>
using namespace std;
pair<int, int> a[10005];
int main() {
  int n, i, cnt = 0, j, x, y, x1, y1, r;
  cin >> r >> x >> y >> x1 >> y1;
  double k;
  k = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  k = k / (r << 1);
  n = ceil(k);
  cout << n << endl;
  return 0;
}
