#include<stdlib.h>
#include<math.h>
int main()
{
    float r,x1,y1,x2,y2,s;
    int x;
    scanf("%f %f %f %f %f",&r,&x1,&y1,&x2,&y2);
    s=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    s=s/(2*r);
    if(s>floor(s)) x=floor(s)+1;
    else x=floor(s);
    printf("%d",x);
    /*printf("\n%f",sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
    printf("\n%f",sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))/(2*r));
    printf("\n%d",floor(s));*/
}
