#include<bits/stdc++.h>
using namespace std;
int main(){
string a;
int s=0;
cin>>a;
for(int i=0;i<a.size();i++){
	s=s+(a[i]-48);
}
cout<<s;
	return 0;
}

/**************************************************************
	Problem: 1115
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/