import math

if __name__ == '__main__':
    R=lambda:map(int,raw_input().split())
    r,x,y,x1,y1=R()
    dist=math.sqrt(pow(x1-x,2)+pow(y1-y,2))
    step=2*r
    ans=0
    while dist>0:
        ans+=1
        dist-=step

    print ans