------
## 最终结论
```python
def remove_Occ(s, char):
    first_index = s.find(char)
    last_index = s.rfind(char)
    
    if first_index == -1 or last_index == -1:
        return s  # If the character is not found, return the original string
    
    return s[:first_index] + s[first_index+1:last_index] + s[last_index+1:]

# Test cases
assert remove_Occ("hello","l") == "heo"
assert remove_Occ("abcda","a") == "bcd"
assert remove_Occ("PHP","P") == "H"
```