#include<bits/stdc++.h>
using namespace std;
int shu;
int he=0;
int main()
{
	
	cin>>shu;
	while(shu>0)
	{
		he=he+shu%10;
		shu=shu/10;
	}
	cout<<he;
	
	return 0;
}
/**************************************************************
	Problem: 1960
	User: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/