[varphi (x) = p_1^{k1-1} (p_1-1) imes p_2^{k2-1} (p2-1) imes p_3^{k3-1}(p3-1)
]
[varphi (x) =x imes frac{(p_1-1)}{p_1} imes frac{(p_2-1)}{p_2} imesfrac{(p_3-1)}{p_3}
]
所以求单个欧拉函数，就可以
ll Euler(ll x) {
ll ans = n;
for (ll i = 2; i * i <= n; i++) {
if (n % i == 0) {
ans = ans / i * (i - 1);
while (n % i == 0) n /= i;
}
}
if (n > 1) ans = ans / n * (n - 1);
return ans;
}