#include<stdio.h>

int main()
{
    int r,x1,y1,x2,y2,e;
    double d,ans;
    scanf("%d%d%d%d%d",&r,&x1,&y1,&x2,&y2);
    d=pow(pow(x1-x2,2)+pow(y1-y2,2),0.5);
    ans=d/(2*r);
    e=ans;
    if(e==ans)
        printf("%d",e);
    else
        printf("%d",e+1);
    return 0;
}
