#include <bits/stdc++.h>
using namespace std;
int main(){
    string o;
    cin>>o;
    int sum=0;
    for(int i=0;i<o.size();i++)sum+=o[i]-'0';
    cout<<sum;
    return 0;
}
/**************************************************************
	Problem: 1119
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/