#include <bits/stdc++.h>
using namespace std;
void solveCase();
void preCompute();
void prepare() {
  ios::sync_with_stdio(false);
  cin.tie(0);
}
int main() {
  prepare();
  preCompute();
  solveCase();
}
void solveCase() {
  long long r, x, y, xn, yn;
  long long d2, steps;
  long long d;
  cin >> r >> x >> y >> xn >> yn;
  d2 = (xn - x) * (xn - x) + (yn - y) * (yn - y);
  d = sqrt(d2);
  assert(d * d <= d2 && (d + 1) * (d + 1) > d2);
  if (d * d < d2) d++;
  steps = d / (2 * r);
  if (2 * r * steps < d) {
    steps++;
  }
  cout << steps << endl;
}
void preCompute() {}
