/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		int sum = 0;
        for (int i = 1; i < 100; i++)
        {
            if (i % 3 != 0) sum += i;
            if (sum > 2000) break;
        }
        System.out.println(sum);
	}
}

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