#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, j, x, y, x1, y1, p = 0, r, l, d;
  double k, mx, n, m;
  scanf("%I64d", &r);
  scanf("%I64d%I64d", &x, &y);
  scanf("%I64d%I64d", &x1, &y1);
  mx = (x - x1) * (x - x1) + (y - y1) * (y - y1);
  n = sqrt(mx);
  d = 2 * r;
  while (m < n) {
    m += d;
    p++;
  }
  printf("%I64d ", p);
  return 0;
}
