#include <bits/stdc++.h>
using namespace std;
const long double eps = 1e-10L;
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long t;
  t = 1;
  while (t--) {
    long long r, x, y, xx, yy;
    cin >> r >> x >> y >> xx >> yy;
    long long d = (x - xx) * (x - xx) + (y - yy) * (y - yy);
    long double dd = sqrt(1.0L * d);
    r = r + r;
    long double res = dd / (1.0L * r);
    long long p = (long long)res;
    if (fabs(1.0L * p * 1.0L * r - dd) > eps) p++;
    cout << p << endl;
    return 0;
  }
  return 0;
}
