#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const long long INF = 1e18 + 107;
const int N = 50 + 107;
int dx[4] = {-1, 0, 0, 1};
int dy[4] = {0, -1, 1, 0};
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int r, x, y, x1, y1;
  cin >> r >> x >> y >> x1 >> y1;
  r *= 2;
  double pml = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  int p = floor(pml);
  cout << p / r + (pml != r * (p / r));
  return 0;
}
