Maximum Displacement

The first line of input contains a string Str, representing the sequence of commands.

The second line contains an integer N, representing the exact number of commands that must be changed.

Print a single integer representing the maximum absolute displacement achievable.

To achieve the maximum positive displacement, you should prioritize changing 'R's to 'S's. If you run out of 'R's to change but still have changes left, you'll be forced to make suboptimal changes ('S' to 'R'). A similar logic applies to achieving the maximum negative displacement. The final answer is the larger of these two possible absolute outcomes.

Sample Input 1:

SRSR
1

Sample Output 1:

2

Explanation for Sample 1:

The string is "SRSR" (2 'S', 2 'R'). We must make N=1 change.
  To maximize positive displacement: Change one 'R' to an 'S'. The new string could be "SSSR". The final position is 3 - 1 = 2.
  To maximize negative displacement: Change one 'S' to an 'R'. The new string could be "RRSR". The final position is 1 - 3 = -2.
The absolute displacements are |2| = 2 and |-2| = 2. The maximum is 2.

Sample Input 2:

S
1

Sample Output 2:

1

Explanation for Sample 2:

The string is "S" (1 'S', 0 'R'). We must make N=1 change.       The only possible change is 'S' to 'R'.
The new string is "R". The final position is -1.
The maximum absolute displacement is |-1| = 1.

Expected Time Complexity:

The expected time complexity is O(N).

Constraints:

1 <= length of Str <= 10^5
0 <= N <= length of Str

Time limit: 1 sec