#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>

int main()
{
    double r,x1,y1,x2,y2;
    while(scanf("%lf%lf%lf%lf%lf",&r,&x1,&y1,&x2,&y2)!=EOF)
    {
        double aa = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
        int tt = 0;
        if(aa==0)
        {
            printf("0\n");
        }
        else if(aa<=2*r)
        {
            printf("1\n");
        }
        else
        {
            while(aa>2*r)
            {
                aa=aa-2*r;
                tt++;
            }
            printf("%d\n",tt+1);
        }
    }
    return 0;
}