#include <bits/stdc++.h>
using namespace std;
pair<int, int> p[105];
int main() {
  double r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  r *= 2;
  double l;
  l = sqrt(abs(x - x1) * abs(x - x1) + abs(y - y1) * abs(y - y1));
  l /= r;
  if (l == int(l)) {
    cout << l;
  } else
    cout << int(l + 1);
}
