# -*- coding:utf-8 -*-
import sys
import math

def some_func():
    """
    """


    r,x,y,x0,y0 = map(int,sys.stdin.readline().split())

    dac = (y0-y)**2+(x0-x)**2
    print int( math.ceil(dac**0.5/(r*2)))






if __name__ == '__main__':
    some_func()





