Multiples of 3 or 5

This is the HackerRank version of Euler Project problem #1.

Problem

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below N.

Input Format

First line contains T that denotes the number of test cases. This is followed by T lines, each containing an integer, N.

Constraints

1 <= T <= 10
1 <= N <= 10

Output Format

For each test case, print an integer that denotes the sum of all the multiples of 3 or 5 below N.

Solution

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Problem1 {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    long t = in.nextLong();
    for (int a0 = 0; a0 < t; a0++) {
      long n = in.nextLong();
      long a = 0, b = 0, c = 0;

      // (n-1) because sum BELOW n, %3 removes remainder
      // on the next line;
      // /3 gets # of 3 multiples
      a = (n-1) % 3;
      a = n - 1 - a;
      a = a / 3;

      b = (n-1) % 5;
      b = n - 1 - b;
      b = b / 5;

      c = (n-1) % 15;
      c = n - 1 - c;
      c = c / 15;

      // Add formulae of each segment and subtract duplicates
      long total = 3*a*(a+1)/2 + 5*b*(b+1)/2 - 15*c*(c+1)/2;
      System.out.println(total);
    }
  }
}