#include <bits/stdc++.h>
long long i, j;
using namespace std;
void solve() {
  long long x, x1, y, y1, r;
  double a, b, c;
  cin >> r >> x >> y >> x1 >> y1;
  a = 1.0 * (x - x1) * (x - x1);
  b = 1.0 * (y - y1) * (y - y1);
  c = sqrt(a + b);
  int dist = ceil((c) / (2 * r));
  cout << dist << endl;
}
int main() { solve(); }
