Method multiply

src/class141/Code01_CRT.java:66–78

(long a, long b, long mod)

	// 讲解033 - 位运算实现乘法
	// a*b过程每一步都%mod，这么写是防止溢出，也叫龟速乘
	public static long multiply(long a, long b, long mod) {
		a = (a % mod + mod) % mod;
		b = (b % mod + mod) % mod;
		long ans = 0;
		while (b != 0) {
			if ((b & 1) != 0) {
				ans = (ans + a) % mod;
			}
			a = (a + a) % mod;
			b >>= 1;
		}
		return ans;
	}

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));