- Time limit: 1.50 s
- Memory limit: 512 MB
Uolevi goes to check up on Maija as she hasn't shown up in the tin foil hat club's gatherings in weeks. He finds her alone in a dark room, smearing her face against a red wall.
Maija has gone down the rabbithole trying to prove the existence of Illuminati. On her leads list board she has n pins and so much red yarn connecting them to one another that the blurry photos and old documents behind them can barely be seen. In this disoriented state, she has started counting the number of triangles formed by the yarn.
Uolevi decides to calculate the number of triangles where the end points are pins, tell Maija that number and then drag her out to get some fresh air. Help Uolevi calculate that number.
Input
The first line contains a single integer n. The i-th of next n lines contains a string s_i.
The j-th character of s_i is "1" if there is yarn connecting pins i and j and "0" otherwise.
Output
Print the number of triangles.
Constraints
- 1 \leq n \leq 3000
- |s_i| = n
- s_{i,j} \in \{0, 1\}
- s_{i, i} = 0
- s_{i, j} = s_{j, i}
Example 1
Input:
4 0111 1001 1001 1110
Output:
2
Example 2
Input:
5 01110 10111 11011 11101 01110
Output:
7