#include <bits/stdc++.h>
using namespace std;
int main() {
  long int data[5];
  int i, counter = 0;
  long long int m = 0, sub1 = 0, sub2 = 0, sum = 0;
  long long int t;
  for (i = 0; i < 5; i++) {
    scanf("%l", &data[i]);
  }
  if (data[1] == data[3] && data[2] == data[4]) {
    cout << 0 << endl;
  } else {
    sub1 = pow((data[1] - data[3]), 2);
    sub2 = pow((data[2] - data[4]), 2);
    t = sqrt(sub1 + sub2);
    m = t - data[0];
    if (m > 0) {
      while (m > 0) {
        m = m - data[0];
        counter++;
      }
    } else {
      while (m < 0) {
        m = m + data[0];
        counter++;
      }
    }
    cout << counter << endl;
  }
  return 0;
}
