#include<bits/stdc++.h>
using namespace std;
int main(){
	char a[300];
	int i,s=0;
	cin>>a;
	for(i=0;i<strlen(a);i++){
		s+=(a[i]-'0');
	}
	cout<<s;
}
/**************************************************************
	Problem: 1115
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/