题目描述Description

Bobo has a decimal integer \(\overline{a_{1} a_{2} \dots a_{n}}\), possibly with leading zeros. He knows that for \(m\) ranges \([l_1, r_1], [l_2, r_2], \dots, [l_m, r_m]\), it holds that \(a_{l_i} \times a_{l_i + 1} \times \dots \times a_{r_i} \bmod 9 = 0\). Find the number of valid integers \(\overline{a_1 a_2 \dots a_n}\), modulo \((10^9+7)\).

输入格式Input

The input consists of several test cases and is terminated by end-of-file.

The first line of each test case contains two integers \(n\) and \(m\).

The \(i\)th of the following \(m\) lines contains two integers \(l_i\) and \(r_i\).

• \(1 \leq n, m \leq 50\)
• \(1 \leq l_i \leq r_i \leq n\)
• There are at most \(100\) test cases.

输出格式Output

For each test case, print an integer which denotes the result.

样例Sample

出题Author

ftiasch

来源Source