#include <bits/stdc++.h>
using namespace std;
const long double pi = 3.14159265359;
const long long MAXN = 1e6 + 9;
const long long mdl = 1000000007LL;
int v[1000000], f[1000000];
int main() {
  double x, y, x1, y1, r, ln = 0;
  cin >> r >> x >> y >> x1 >> y1;
  ln = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
  cout << ceil(ln / (r * 2));
}
