#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, aa, bb, ct, qq, d, r;
  float q;
  cin >> r >> a >> b >> aa >> bb;
  q = (aa - a) * (aa - a);
  q = q + (bb - b) * (bb - b);
  q = sqrt(q);
  qq = q;
  d = r * 2;
  if (q >= d || (a == aa && b == bb)) {
    if (q - qq == 0) {
    } else {
      qq++;
    }
    if (qq % d == 0)
      cout << qq / d;
    else
      cout << qq / d + 1;
  } else {
    cout << "1";
  }
  return 0;
}
