#include <bits/stdc++.h>
using namespace std;
long long int scan() {
  long long int t = 0;
  char c, ch;
  ch = getchar();
  if (ch == '-') {
    c = getchar();
  } else {
    c = ch;
  }
  while (c < '0' || c > '9') {
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    t = (t << 3) + (t << 1) + c - '0';
    c = getchar();
  }
  if (ch == '-') {
    return -t;
  } else {
    return t;
  }
}
int main() {
  ios::sync_with_stdio(false);
  long long int i, j, k, t, n, m, x, y, a, b, r;
  cin >> r >> x >> y >> a >> b;
  n = abs(x - a);
  m = abs(y - b);
  long long dis = n * n + m * m, ans = 0;
  if (dis == 0)
    cout << "0\n";
  else if (dis <= (r * r)) {
    cout << "1\n";
  } else {
    double val = sqrt(dis);
    ans = val / (2 * r);
    if (ans * 2 * r != val) ans++;
    cout << ans << "\n";
  }
  return 0;
}
