#include <bits/stdc++.h>
using namespace std;
inline string IntToStr(int x) {
  ostringstream ss;
  ss << x;
  return ss.str();
}
inline int StrToInt(string x) {
  int i;
  istringstream iss(x);
  iss >> i;
  return i;
}
long long r, x, y, xx, yy;
inline int solve() {
  double dist = (xx - x) * (xx - x) + (yy - y) * (yy - y);
  dist = sqrt(dist);
  dist /= 2 * r;
  return ceil(dist);
}
int main() {
  scanf("%I64d  %I64d  %I64d  %I64d  %I64d", &r, &x, &y, &xx, &yy);
  printf("%d\n", solve());
  return 0;
}
