# Triangle, pentagonal, and hexagonal numbers are generated by the following formulae:
#
# Triangle	 	Tn=n(n+1)/2	 	1, 3, 6, 10, 15, ...
# Pentagonal	 	Pn=n(3n−1)/2	 	1, 5, 12, 22, 35, ...
# Hexagonal	 	Hn=n(2n−1)	 	1, 6, 15, 28, 45, ...
# It can be verified that T285 = P165 = H143 = 40755.
#
# Find the next triangle number that is also pentagonal and hexagonal.


from math import sqrt


def is_pentagonal(n):
    k = (1 + sqrt(1 + 24 * n)) / 6
    return k == int(k)


def is_hexagonal(n):
    k = (1 + sqrt(1 + 8 * n)) / 4
    return k == int(k)


def triangle(k):
    return k * (k + 1) / 2


k = 286
while True:
    n = triangle(k)
    if is_pentagonal(n) and is_hexagonal(n):
        print(n)
        break
    k += 1