#include <bits/stdc++.h>
int main() {
  long long r, x1, y1, x2, y2;
  while (~scanf("%I64d %I64d %I64d %I64d %I64d", &r, &x1, &y1, &x2, &y2)) {
    double t = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    printf("%d\n", (int)ceil(t / (2 * r)));
  }
  return 0;
}
