from math import floor


def next_b(b_prev):
    b = floor(b_prev) * (b_prev - floor(b_prev) + 1)
    return b


def euler_751():

    min_found = 2
    theta_str_orig = "2."
    while len(theta_str_orig) < 26:
        for n in range(min_found, 1000):
            theta_str_new = str(theta_str_orig) + str(n)
            b = float(theta_str_new)
            theta_str = theta_str_new.replace("2.", "")
            while theta_str != "":
                b = next_b(b)
                a_str = str(floor(b))
                # print(a_str, theta_str)
                if theta_str.startswith(a_str):
                    theta_str = theta_str.replace(a_str, "", 1)
                else:
                    break
            if theta_str == "":
                theta_str_orig = theta_str_new
                break
    return theta_str_orig


if __name__ == "__main__":
    solution = euler_751()
    print("e751.py: " + str(solution))
    assert solution == "2.223561019313554106173177"