#include <bits/stdc++.h>
int x, y, xc, yc, r;
double dist;
int step;
int main() {
  scanf("%d%d%d%d%d", &r, &x, &y, &xc, &yc);
  dist = sqrt((long double)((long long)xc - x) * (xc - x) +
              ((long long)yc - y) * (yc - y));
  step = dist / (r << 1);
  if (step * (r << 1) < dist) step++;
  printf("%d", step);
  return 0;
}
