package main

import (
    "strings"
    "fmt"
    "strconv"
)

func main() {
	var input string
	var result int
	fmt.Scan(&input)
	var data = strings.Split(input, "")
	for _, s := range data {
	    n, _ := strconv.Atoi(s)
	    result += n
	}
	fmt.Println(result)
}