题解 | #小乐乐与字符串#

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        String s = sc.next();
        long c = 0;
        long h = 0;
        long n = 0;
        for(int i = 0 ; i < s.length() ; i++) {
            if(s.charAt(i) == 'C') {
                c++;
            } else if(s.charAt(i) == 'H') {
                h += c;
            } else if(s.charAt(i) == 'N') {
                n += h;
            }
        }
        System.out.println(n);
    }
}