#include<bits/stdc++.h>
using namespace std;
int main(){
    string s;
    cin>>s;
    int r=0;
    for(int i=0;i<s.size();i++){
        r+=s[i]-'0';
    }
    cout<<r;
    return 0;
}
/**************************************************************
	Problem: 1115
	User: luyanchen
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2076 kb
****************************************************************/