#include<stdio.h>
#include<stdlib.h>
int main()
{
    double r,x1,y1,x2,y2,ans,tot,d;
    int ansf;
    scanf("%lf %lf %lf %lf %lf",&r,&x1,&y1,&x2,&y2);
    tot=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    //printf("%lf ",tot);
    d=2*r;
    ans=tot/d;
    //printf("%lf ",ans);
    ansf=(ans+0.99999999);
    printf("%d",ansf);
    return 0;
}