#include <bits/stdc++.h>
int rt(int n) {
  int i;
  for (i = 0; i * i <= n; i++)
    ;
  if ((i - 1) * (i - 1) == n)
    return i - 1;
  else
    return i;
}
int main() {
  int r, x, y, nx, ny, flag = 0;
  scanf("%d%d%d%d%d", &r, &x, &y, &nx, &ny);
  int temp = (nx - x) * (nx - x) + (ny - y) * (ny - y);
  int root = rt(temp);
  int moves = root / (2 * r);
  if (moves * 2 * r == root)
    printf("%d\n", moves);
  else
    printf("%d\n", moves + 1);
  return 0;
}
