#include <bits/stdc++.h>
using namespace std;
long long power(long long x, long long n) {
  long long res = 1;
  while (n) {
    if (n & 1) res = (res * x);
    x = (x * x);
    n >>= 1;
  }
  return res;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  long long r, a, b, x, y;
  cin >> r >> a >> b >> x >> y;
  long long d = ((x - a) * (x - a)) + ((y - b) * (y - b));
  long long ck = sqrt(d);
  long long ans = (ck / (2 * r));
  if (ck * ck != d)
    cout << ans + 1;
  else {
    if (ans * 2 * r == ck)
      cout << ans;
    else
      cout << ans + 1;
  }
}
