#include <bits/stdc++.h>
using namespace std;
int main() {
  int r, x, y, X, Y;
  scanf("%d%d%d%d%d", &r, &x, &y, &X, &Y);
  int R = 2 * r;
  int dis = sqrt(pow((X - x), 2) + pow((Y - y), 2));
  int pin = 0;
  if (dis >= r) {
    dis -= r;
    pin++;
  }
  pin += (dis / R);
  if (dis % R) pin++;
  printf("%d\n", pin);
}
