#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-8;
double R, X, Y, Xp, Yp;
int main() {
  cin >> R >> X >> Y >> Xp >> Yp;
  if (X == Xp && Y == Yp) {
    cout << 0 << endl;
    return 0;
  }
  double dx = X - Xp, dy = Y - Yp;
  double d = sqrt(dx * dx + dy * dy) - EPS;
  int n = (int)(d + 2 * R) / (2 * R);
  cout << n << endl;
  return 0;
}
