#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <ctime>
#include <string>
#include <ctime>
#include <set>
#include <functional>
#include <map>
#include <vector>
using namespace std;

long  r, x, y, t_x,t_y, dct, rest;
int main()
{
#ifdef _DEBUG
    clock_t tt;
    tt = clock();
    freopen("1.in", "rt", stdin);
    freopen("1.out", "wt", stdout);
#endif
    while(scanf("%ld %ld %ld %ld %ld\n%", &r, &x, &y, &t_x, &t_y)!=EOF)
	{
		dct = (x - t_x)*(x - t_x) + (y-t_y)*(y-t_y);
		rest = sqrt((long double)dct);
		rest +=(rest * rest == dct ?0:1);
		printf("%ld\n", rest/(r*2) + (rest%(r*2)?1:0));
    }
#ifdef _DEBUG
    tt = clock() - tt;
    float time = ((float)tt) / CLOCKS_PER_SEC;
    std::cout << time;
#endif
    return 0;
}