#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int r, x, y, xf, yf;
void in(int &x) {
  bool neg = false;
  register int c;
  x = 0;
  c = getchar();
  if (c == '-') {
    neg = true;
    c = getchar();
  }
  for (; c > 47 && c < 58; c = getchar()) x = (x << 1) + (x << 3) + c - 48;
  if (neg) x *= -1;
}
int main() {
  in(r);
  in(x);
  in(y);
  in(xf);
  in(yf);
  double dx = abs(xf - x), dy = abs(yf - y);
  double d = sqrt(dx * dx + dy * dy);
  printf("%d", (int)ceil(d / (2 * r)));
  return 0;
}
