#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <queue>
#include <set>
using namespace std;
typedef long long ll;
ll n,h;
ll ret;
int r,x1,y,x2,y2;
int main() {
    while(cin>>r>>x1>>y>>x2>>y2)
    {
        double temp = pow(((x2-x1)*(x2-x1))+((y-y2)*(y-y2)),0.5);
        double temp1 = 2*r;
        ll ret =  ceil((temp*1.0/temp1));
        cout<<ret<<endl;
    }
    return 0;
}
