4432: String Commutativity

Bobo has n strings s₁, ..., s_n, and he would like to find the number of pairs i < j where s_i + s_j = s_j + s_i.

Note that a + b means the concatenation of the string a and b, i.e., writing the string a first, and the string b second.

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

The first line of each test case contains an integer n. The i-th of the following n lines contains a string s_i.

• 1 ≤ n ≤ 10⁵
• |s_i| ≤ 10⁶, s_i contains only lower case characters.
• The sum of strings does not exceed 5 × 10⁶.

2
a
ab
2
ab
ab
3
a
aa
aaa

0
1
3