r, x1,y1,x2,y2 = map(int, raw_input().split())
dist = ((((x1-x2)**2) + ((y1-y2)**2))**(1.0/2.0))-2*r
qnt = 1

while(dist>0):
    qnt += 1
    dist -= 2*r

if(x1==x2 and y1==y2):
    print 0
else:
    print qnt