nakkaa

import { Injectable } from '@nestjs/common';
import { checkWordMute } from '@/misc/check-word-mute.js';
import { isUserRelated } from '@/misc/is-user-related.js';
import type { Packed } from '@/misc/json-schema.js';
import { MetaService } from '@/core/MetaService.js';
import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
import { bindThis } from '@/decorators.js';
import { RoleService } from '@/core/RoleService.js';
import Channel from '../channel.js';

nakkaa

def ex2019a():
    n = raw_input().split(" ")
    a = int(n[0])
    b = int(n[1])
    c = int(n[2])

    if a == b and b == c:
        print "Yes"
    else:
        print "No"

nakkaa

def ex2019b():
    N = int(raw_input())
    S = raw_input()
    s = list(S)

    r = 0
    b = 0

    for i in range(N):
        if s[i] == "R":

nakkaa

def abc081():
    s = raw_input()
    cnt = 0
    if s[0] == '1': cnt += 1
    if s[1] == '1': cnt += 1
    if s[2] == '1': cnt += 1
    print cnt

def main():
    abc081()