------
## 最终结论
```python
def first_Element(arr, n, k):
    count = {}
    for num in arr:
        if num in count:
            count[num] += 1
        else:
            count[num] = 1
        
        if count[num] == k:
            return num
    return None

# Test cases
assert first_Element([0,1,2,3,4,5],6,1) == 0
assert first_Element([1,2,1,3,4],5,2) == 1
assert first_Element([2,3,4,3,5,7,1,2,3,5],10,2) == 2
```