------
## 最终结论
```python
def can_measure_water(x, y, z):
    if z > x + y:
        return False
    if z % gcd(x, y) == 0:
        return True
    return False

def gcd(a, b):
    while b:
        a, b = b, a % b
    return a

# Example usage:
print(can_measure_water(3, 5, 4))  # Output: True
print(can_measure_water(2, 6, 5))  # Output: False
```