The function swaps every pair of adjacent characters in the input string. If the length of the string is odd, the last character remains in place.

[CODE]: 
```python
def approx_function(s):
    result = ""
    for i in range(0, len(s)-1, 2):
        result += s[i+1] + s[i]
    if len(s) % 2 != 0:
        result += s[-1]
    return result
```