#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int r, x1, y1, x2, y2;
  cin >> r >> x1 >> y1 >> x2 >> y2;
  float dist;
  dist = sqrt(((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2)));
  if (dist == 0) {
    printf("0\n");
    return 0;
  }
  if (fmod(dist, (2.0 * r)) == 0)
    printf("%I64d\n", ((long long int)dist / (2 * r)));
  else
    printf("%I64d\n", 1 + ((long long int)dist / (2 * r)));
  return 0;
}
