#include<bits/stdc++.h>
using namespace std;
int main(){
    int c=0;
    string s;
    cin>>s;
    for(int i=0;i<s.size();i++){
    	c=c+(s[i]-'0');
    }
    cout<<c;
    return 0;
}

/**************************************************************
	Problem: 1115
	User: linyuhang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/