#include<bits/stdc++.h>
using namespace std;
int main(){
    string n;
    cin>>n;
    int n2=n.size(),s=0;
    for(int i=0;i<n2;i++)
    {
        s+=n[i]-'0';
    }
    cout<<s;
}
/**************************************************************
	Problem: 1115
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/