Problem10421-- USACO 2023 December Contest, Silver Problem 3. Target Practice

10421: USACO 2023 December Contest, Silver Problem 3. Target Practice

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Time Limit : 1.000 sec  Memory Limit : 512 MiB

Description

Bessie is a robovine, also known as a cowborg. She is on a number line trying to shoot a series of $T\ (1≤T≤10^5)$ targets located at distinct positions. Bessie starts at position 00 and follows a string of $C\ (1≤C≤10^5)$ commands, each one of L, F, or R:

  • L: Bessie moves one unit to the left.
  • R: Bessie moves one unit to the right.
  • F: Bessie fires. If there is a target at Bessie's current position, it is hit and destroyed, and cannot be hit again.

If you are allowed to change up to one command in the string to a different command before Bessie starts following it, what is the maximum number of targets that Bessie can hit?

Input

The first line contains $T,C$.

The next line contains the locations of the $T$ targets, distinct integers in the range $[−C,C]$.

The next line contains the command string of length $C$, containing only the characters F, L, and R.

Output

Print the maximum number of targets that Bessie can hit after changing up to one command in the string.

Sample 1 Input

3 7
0 -1 1
LFFRFRR

Sample 1 Output

3

If you make no changes to the string, Bessie will hit two targets:

Command 
Position 
Total Targets Hit
Start
0 0
L -1 0
F -1
1
F -1
1 (can't destroy target more than once)
R 0 1
F 0 2
R 1 2
R 2 2

If you change the last command from R to F, Bessie will hit all three targets:

Command 
Position 
Total Targets Hit
Start
0 0
L -1 0
F -1
1
F -1
1 (can't destroy target more than once)
R 0 1
F 0 2
R 1 2
F 1 3

Sample 2 Input

1 5
0
FFFFF

Sample 2 Output

1
If the commands are left unchanged, the only target at 0 will be destroyed. Since a target cannot be destroyed multiple times, the answer is 1.

Sample 3 Input

5 6
1 2 3 4 5
FFRFRF

Sample 3 Output

3

HINT

Source/Category