#include<bits/stdc++.h>
using namespace std;
int main()
{
    string a;
    int n=0;
    cin>>a;
    for(int i=0;i<a.size();i++)
    {
        n=n+(a[i]-48);
    }
    cout<<n;
    return 0;
}
/**************************************************************
	Problem: 1115
	User: wengsihan
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/