Is it divisible?
Problem
Question is pretty straight-forward.
You are given a set of 'n' numbers. You need to find total pairs of numbers whose sum is divisible by 5.
Note: Pair of numbers means collection of any two numbers from the set.
See sample test-case for more understanding.
Input format:
First line consist of total numbers given as 'n'.
Next Line consists of 'n' numbers seperated by space.
Output format:
Output total pairs whose sum is divisible by 5.
Constraints:
1 <= n <= 10^6
1 <= number <= 10^6
Time Limit: 1
Memory Limit: 256
Source Limit:
Explanation
Total pairs possible in this test-case are: (1, 2), (1, 3) and (2, 3).
(1, 2) --> 1 + 2 == 3 (not divisible by 5)
(1, 3) --> 1 + 3 == 4 (not divisible by 5)
(2, 3) --> 2 + 3 == 5 (divisible by 5)
Hence, answer is 1 as only one pair has a sum divisible by 5.
