import java.util.ArrayList;
import java.util.Scanner;

/**
 *How to put out the hands of rock-paper-scissors(equivalent to paiza rank A)
 */
public class AS001{

	public static void main(String[] args) {

		//input
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		char[] handArray = sc.next().toCharArray();


		//Opponent hand analysis
		int[] handCount = new int[3]; //{G, C, P}
		for(char hand : handArray) {
			switch(hand) {
			case 'G':
				handCount[0]++;
				break;
			case 'C':
				handCount[1]++;
				break;
			case 'P':
				handCount[2]++;
				break;
			}//switch
		}//for


		//Hand pattern enumeration
		ArrayList<Integer[]> patternList = new ArrayList<>(100);
		for(int i = 0; i <= n; i++) {
			for(int j = 0; j <= n; j++) {
				int yubi = i * 2 + j * 5; //index
				int remain = n - i - j; //Number of remaining games

				if(yubi == m && remain >= 0) {
					//A combination that uses up your fingers within the total number of games
					Integer[] pattern = {remain, i, j}; //{g, c, p}
					patternList.add(pattern);
				}else if(yubi > m || remain < 0) {
					//If the number of games is used up or the index is exceeded, the next loop
					break;
				}//if
			}//for
		}//for


		//Calculate the pattern of maximum wins
		int maxWin = 0;
		for(Integer[] pattern : patternList) {
			int win = 0;
			win += Math.min(handCount[0], pattern[2]); //The other party is goo, I am par
			win += Math.min(handCount[2], pattern[1]); //The other party is par, I am choki
			win += Math.min(handCount[1], pattern[0]); //The other party is Choki, I am Goo
			if(win > maxWin) maxWin = win;
		}//for


		//output
		System.out.println(maxWin);
	}//main
}//class

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