import math
r,a,b,x,y=map(int,input().split())
dis=math.sqrt((a-x)**2+(b-y)**2)
count=0
while(True):
    if(dis==0):
        break
    elif(dis<=r):
        count+=1
        break
    elif(dis>r and dis<2*r):
        count+=1
        break
    elif(dis>=2*r):
        dis-=2*r
        count+=1
print(count)        