#include <bits/stdc++.h>
using namespace std;
int n, m;
double absx(double x) {
  if (x > 0)
    return x;
  else
    return -x;
}
double sqr(double x) { return x * x; }
bool leq(double a, double b) { return a < b || absx(a - b) < 1e-8; }
int r, x, y, xx, yy;
int main() {
  cin >> r >> x >> y >> xx >> yy;
  if (x == xx && y == yy) {
    cout << 0 << endl;
    return 0;
  }
  int ans = 0;
  double d = sqrt(sqr(x - xx) + sqr(y - yy)) / 2 / r;
  cout << ceil(d) << endl;
}
