Given three strings S, oldW and newW. Find all occurrences of the word oldW in S and replace them with word newW.

Example 1:

Input: 
S = "xxforxx xx for xx"
oldW = "xx"
newW = "Geeks"
Output: 
"geeksforgeeks geeks for geeks" 
Explanation: 
Replacing each "xx" with
"Geeks" in S.

Example 2:

Input: 
S = "india is the xx country"
oldW = "xx"
newW = "best"
Output: 
"india is the best country"
Explanation: 
Replacing each "xx" with
"best" in S.

Your Task:  
You dont need to read input or print anything. Complete the function ReplaceAll() which takes S, oldW and newW as input parameters and returns the string S after replacing all oldW with newW.

Expected Time Complexity: O(n²)
Expected Auxiliary Space: O(1)

Constraints:
1<= |S| <=1000
1<= |oldW|, |newW| <=|S|