void phi_table()
{
for (int i = 1; i < maxn; i++) {
phi[i] = i;
}
for (int i = 2; i < maxn; i++) {
if (phi[i] == i) {
for (int j = i; j < maxn; j += i) {
phi[j] = phi[j] / i * (i - 1);
}
}
}
}
Pollard Rho 算法求欧拉函数
ll get_phi(int n)
{
ll res = 1;
for (int i = 2; i <= sqrt(n); i++) {
if (n % i == 0) {
n /= i;
res *= i - 1;
while (n % i == 0) {
n /= i;
res *= i;
}
}
}
if (n > 1) {
res *= n - 1;
}
return res;
}