#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef double dl;
#define sz(x) (int)s.size()
#define pb push_back
#define lp1(i,n) for(int i=0;i<n;i++)
#define lp2(i,n) for(int i=1;i<=n;i++)
#define pi cosa(-1)
ll lcm(ll a,ll b)
{
    return a/__gcd(a,b)*b;
}
ll gcd(ll a,ll b)
{
	while(b ^= a ^= b ^= a = a % b);
	return a;
}
std::string s;
void cin_space()
{

    std::getline(std::cin, s);
}
void sortstring(string &str)
{
   sort(str.begin(), str.end());
}
bool check_prime(ll n)
{
    ll q=sqrt(n)+1;
    for(int i=2;i<q;i++)
        if(n%i==0)
            return 0;
    return 1;
}
ll ceil(ll n,ll k){
    return (n+k-1)/k;
}

void solution()
{
    int r,x,y,x1,y1;
    cin>>r>>x>>y>>x1>>y1;
    float len=sqrt(((x-x1)*(x-x1))+((y-y1)*(y-y1)));
    int ans=ceil(len,r)-1;
    if(ans<=0)
        cout<<0<<endl;
    else
    cout<<ans<<endl;
}

int main() {
   ll t=1;
   //cin>>t;
   while(t--){
    solution();
   }

   return 0;
}
