3. At the hitmen convention, 1000 participants gathered, each receiving a registration number from 1 to 1000. By the end of the convention, it turned out that all hitmen, except number 1, were killed. It is known that each hitman could only kill hitmen with higher numbers, and the number of his victims could not exceed his number. What is the minimum number of hitmen who could have participated in the killings at the convention?
Answer: 10

## Examples of answer notation:

5

#