def readarray(f): return map(f, raw_input().split())
def readint(): return int(raw_input())
def printlist(l): print ' '.join(map(str, l))

r, x, y, xx, yy = readarray(int)

d = ((x-xx)*(x-xx) + (y-yy)*(y-yy))**0.5

import math

print int(math.ceil(d/(2*r)))
