#include <bits/stdc++.h>
long long R = 7 + 1e9, NUMTESTCASE;
const int NN = 10 + 1e5;
const double pi = acos(-1.0);
int di[4] = {1, 0, -1, 0}, dj[4] = {0, 1, 0, -1},
    DI[8] = {1, 1, 0, -1, -1, -1, 0, 1}, DJ[8] = {0, 1, 1, 1, 0, -1, -1, -1};
using namespace std;
int main() {
  long double r, a, b, x, y;
  cin >> r >> a >> b >> x >> y;
  r *= 2;
  cout << ceil(sqrt((x - a) * (x - a) + (y - b) * (y - b)) / r);
  return 0;
}
