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

/**************************************************************
	Problem: 1115
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2076 kb
****************************************************************/