import sys
import math
import bisect

def main():
    r, x1, y1, x2, y2 = map(int, input().split())
    dist = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(math.ceil(dist / (2*r)))

if __name__ == "__main__":
    main()
