#define _USE_MATH_DEFINES
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<sstream>
#include<utility>
#include<map>
#include<climits>
#include<vector>
#include<queue>
#include<algorithm>
#include<set>
#include<stack>
#include<functional>
#include<cmath>
#include<iostream>
using namespace std;
typedef long long ll;
typedef pair<int,int>P;

const ll MOD=1e9+7;
const int INF = 1000000000;

int main()
{
	string s;
	int res=0;
	cin>>s;
	for(int i=0;i<s.size();i++)
	{
		int t=s[i]-'0';
		res+=t;
	}
	cout<<res<<endl;
}