#include <bits/stdc++.h>
long long r, x1, Y1, x2, Y2;
double h;
int main() {
  scanf("%I64d %I64d %I64d %I64d %I64d", &r, &x1, &Y1, &x2, &Y2);
  double dist = sqrt((x1 - x2) * (x1 - x2) + (Y1 - Y2) * (Y1 - Y2));
  printf("%d", (int)ceil(dist / (2 * r) * 1.0));
  return 0;
}
