#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
bool prime[1000001];
void sieve() {
  memset(prime, true, sizeof(prime));
  for (int i = 2; i * i <= 1000000; i++)
    if (prime[i])
      for (int j = i * i; j <= 1000000; j += i) prime[j] = false;
  prime[0] = prime[1] = false;
}
long long int gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int pow(long long int a, long long int b, long long int MOD) {
  long long int x = 1, y = a;
  while (b > 0) {
    if (b % 2 == 1) {
      x = (x * y);
      if (x > MOD) x %= MOD;
    }
    y = (y * y);
    if (y > MOD) y %= MOD;
    b /= 2;
  }
  return x;
}
int main() {
  double r, x, y, xx, yy;
  cin >> r >> x >> y >> xx >> yy;
  double dist = sqrt((x - xx) * (x - xx) + (y - yy) * (y - yy)) / (2 * r);
  if (dist == (long long)dist)
    cout << (long long)dist;
  else
    cout << (long long)dist + 1;
  return 0;
}
