import atexit
import io
import sys
import math as m

# _INPUT_LINES = sys.stdin.read().splitlines()
# input = iter(_INPUT_LINES).__next__
# _OUTPUT_BUFFER = io.StringIO()
# sys.stdout = _OUTPUT_BUFFER
#
#
# @atexit.register
# def write():
#     sys.__stdout__.write(_OUTPUT_BUFFER.getvalue())

R = lambda : map(int,input().split())
r,x,y,x1,y1 = R()

ans = m.ceil((m.sqrt((x-x1)**2+(y-y1)**2))/(2*r))
print(ans)
