------
## 最终结论
```python
def first_even(numbers):
    for num in numbers:
        if num % 2 == 0:
            return num

# Test cases
assert first_even([1, 3, 5, 7, 4, 1, 6, 8]) == 4
assert first_even([2, 3, 4]) == 2
assert first_even([5, 6, 7]) == 6
```