#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: chenyaohuo
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2076 kb
****************************************************************/