'''input
1 1 1 4 4
'''

from math import sqrt, ceil

def dis(x1, y1, x2, y2):
    return sqrt((x1-x2)**2 + (y1-y2)**2)



def main():

   r, x1, y1, x2, y2 = map(int, input().split())

   dist = dis(x1, y1, x2, y2)

   # print(dist)
   # print(dist//(2*r), dist%(2*r))
   print(ceil(dist/(2*r)))







if __name__ == '__main__':
    main()
