"""http://codeforces.com/problemset/problem/507/B"""

def solve(r, xa, ya, xb, yb):
    d = ((xa - xb) ** 2 + (ya - yb) ** 2) ** 0.5
    return -int(-d // (2 * r))

def test():
    f = lambda st: list(map(int, st.split()))
    assert solve(*f('2 0 0 0 4')) == 1
    assert solve(*f('1 1 1 4 4')) == 3
    assert solve(*f('4 5 6 5 6')) == 0

if __name__ == '__main__':
    # test()
    res = solve(*list(map(int, input().split())))
    print(res)
