Add some tests...

Try this test.
5 3 6
1
2
3
4
5
4 5 6
answer : 11

Why 11 but not 12?, please explain, i don't understand that

On first 3 seconds, we pick 1, 2, 3. On 4th second, we drop 1, 2, 3. On 5th and 6th second, we drop nothing. On 7th, 8th, 9th, 10th, 11th second, we pick 1, 2, 3, 4, 5. So the answer is 11.