package main

import (
	"fmt"
)

func main() {
	var s string
	if _, err := fmt.Scan(&s); err != nil {
		return
	}

	m := make(map[rune]int)
	for _, ch := range s {
		m[ch]++
	}

	k := len(m)
	if k == 4 {
		fmt.Println("Yes")
	} else if k == 3 {
		if len(s) >= 4 {
			fmt.Println("Yes")
		} else {
			fmt.Println("No")
		}
	} else if k == 2 {
		ok := true
		for _, v := range m {
			if v < 2 {
				ok = false
			}
		}
		if ok {
			fmt.Println("Yes")
		} else {
			fmt.Println("No")
		}
	} else {
		fmt.Println("No")
	}
}