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

/**************************************************************
	Problem: 1115
	User: yangjunwenredianling
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2076 kb
****************************************************************/