#include <bits/stdc++.h>
const int maxN = 1e6;
using namespace std;
long long r, a, b, x, y;
double dist, res;
void ReadInput() { cin >> r >> a >> b >> x >> y; }
void Process() {
  double dist = sqrt((x - a) * (x - a) + (y - b) * (y - b));
  res = dist / double(r * 2);
  if ((long long)(res) != res) ++res;
}
void WriteOutput() { cout << (long long)res; }
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ReadInput();
  Process();
  WriteOutput();
}
