#include <bits/stdc++.h>
using namespace std;
typedef struct node {
  int val, ind;
} node;
bool operator<(node a, node b) { return a.val < b.val; }
int main() {
  long long r, x, y, x2, y2;
  cin >> r >> x >> y >> x2 >> y2;
  double min_dist = sqrt(pow(x - x2, 2) + pow(y2 - y, 2));
  r = r * 2;
  cout << ceil(min_dist / r) << endl;
  return 0;
}
