#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int f = 1, x = 0;
  char ch;
  do {
    ch = getchar();
    if (ch == '-') f = -1;
  } while (ch < '0' || ch > '9');
  do {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  } while (ch >= '0' && ch <= '9');
  return f * x;
}
int r, x, y, px, py;
int main() {
  scanf("%d%d%d%d%d", &r, &x, &y, &px, &py);
  double dis = sqrt(1.0 * (x - px) * (x - px) + 1.0 * (y - py) * (y - py));
  printf("%d\n", (int)(ceil(1.0 * dis / (2.0 * r))));
}
