#include <bits/stdc++.h>

using namespace std;

int r;
int x1,x2,y1,y2;

int main (){
    cin>>r>>x1>>y1>>x2>>y2;
    cout<<(int)ceil(sqrt(abs(x1-x2)*abs(x1-x2)+abs(y1-y2)*abs(y1-y2))/(2*r))<<endl;
    return 0;
}
