#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
const int mod = 1000000007;
using namespace std;
double disBetPoi(int x1, int y1, int x2, int y2) {
  double dis = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
  return dis;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  double disInOne = r * 2;
  if (x1 == x2 && y1 == y2)
    cout << 0 << endl;
  else {
    double dis = disBetPoi(x1, y1, x2, y2);
    int steps = ceil(dis / disInOne);
    cout << steps << endl;
  }
  return 0;
}
