#include <bits/stdc++.h>
using namespace std;
long long a, c, i, j, k, x, y, z;
double b;
int main() {
  cin >> a >> x >> y >> i >> j;
  b = (x - i) * (x - i) + (y - j) * (y - j);
  b = sqrt((double)b);
  k = b / (2 * a);
  b -= (k * 2 * a);
  if (b == 0)
    cout << k << endl;
  else
    cout << k + 1 << endl;
  return 0;
}
