#include <bits/stdc++.h>
using namespace std;
int main() {
  int x[5];
  for (int i = 0; i < 5; i++) {
    cin >> x[i];
  }
  double c = (x[1] - x[3]) * (x[1] - x[3]) + (x[2] - x[4]) * (x[2] - x[4]);
  c = sqrt(c);
  x[0] = 2 * x[0];
  c = c / x[0];
  if (fmod(c, 1))
    cout << (int)c + 1;
  else
    cout << c << endl;
}
