#include <bits/stdc++.h>
int main() {
  long long int r, x, y, x1, y1, i, j, k, d;
  double df;
  scanf("%I64d %I64d %I64d %I64d %I64d\n", &r, &x, &y, &x1, &y1);
  df = sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
  d = (int)floor(df);
  if (d != df) {
    printf("%I64d ", (d / (2 * r)) + 1);
    return 0;
  }
  if (d % (2 * r) == 0)
    printf("%I64d", d / (2 * r));
  else
    printf("%I64d", d / (2 * r) + 1);
}
