Digital Divination (APCS 2022-01 Advanced)

2.0s 256M

Given \(m\) distinct lowercase strings, count unordered pairs of different strings whose concatenation is \(XX\) for some nonempty string \(X\). Swapping the strings does not create another pair.

Input

Read \(m\), followed by one string per line.

Constraints

\(1\le m\le50000\); string lengths are between \(1\) and \(100\).

Output

Print the number of qualifying pairs.

Scoring

Each scored test independently awards 5 points, totaling 100. Samples award no points.

  • 1: 20% — \(2\le m\le100\); lengths are \(10\) or \(20\).
  • 2: 20% — Lengths are \(10\) or \(20\).
  • 3: 60% — No additional restrictions.

Sample Input 1

3
a
aba
aaa

Sample Output 1

1

Sample Input 2

5
abyyyab
y
yy
yyy
yyyy

Sample Output 2

3

Source

h083 · 2022-01 APCS.

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