#include <bits/stdc++.h>
using namespace std;
int main(){
	string s;
	cin>>s;
	cout<<s[0]-'0'+s[1]-'0'+s[2]-'0';
}

/**************************************************************
	Problem: 1027
	User: zhouhongyi
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/