DMOPC '20 Contest 3 P2 - Bob and Parallel-Ks
View as PDFBob is composing a song for  singers to perform! The song lasts for 
 beats, and the 
-th singer is assigned a series of 
 notes 
 to sing on each of the beats. Notes are represented by integer values, and the 
 notes sung on a single beat are all distinct.
Unfortunately, Bob needs to watch out for parallel-s. A parallel-
 is a triple 
 such that 
. In other words, a parallel-
 is two singers 
 and 
, plus a beat 
, such that the notes that 
 and 
 sing form an interval of 
 on both beats 
 and 
.
Parallel-s make music sound absolutely horrendous (for some reason), so please help Bob find all the parallel-
s in his song!
Constraints
For a given , 
 are distinct.
Subtask 1 [2/15]
Subtask 2 [5/15]
Subtask 3 [8/15]
Input Specification
The first line contains three space-separated integers: , 
, and 
.
The next  lines each contain 
 space-separated integers, 
, the notes sung on each beat by singer 
.
Output Specification
The number of distinct parallel-s in Bob's song. (Two parallel-
s 
 and 
 are distinct if 
, or 
, or 
.)
Sample Input
5 3 5
5 6 6
10 11 11
15 16 16
105 116 118
110 111 113
Sample Output
5
Explanation for Sample Output
Singers 1 and 2 form two parallel-5s: one between beats 1 and 2, and another between beats 2 and 3. Singers 2 and 3 also form two parallel-5s. Finally, singers 5 and 4 form one parallel-5 between beats 2 and 3. In total, there are five parallel-5s: , 
, 
, 
, and 
. (Note that 
, 
, and 
 do not fit the definition of a parallel-5.)
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