GuntingBatuKertas - TOKI

import java.util.*;

/*
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/**
 *
 * @author nur
 */
public class GuntingBatuKertas {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n;
        String s1, s2;
        Map<String, String> libs = new HashMap<>();

        libs.put("G", "K");
        libs.put("B", "G");
        libs.put("K", "B");

        n = sc.nextInt();

        s1 = sc.next();
        s2 = sc.next();

        int result = 0;
        for (int j = 0; j < s1.length(); j++) {
            String cur = String.valueOf(s1.charAt(j));
            String toCheck = libs.get(cur);

            int index = s2.indexOf(toCheck);
            if (index != -1) {
                result++;
                s2 = s2.substring(0, index) + s2.substring(index + 1);
            }

        }
        System.out.println(result);

    }
}