#include <bits/stdc++.h> 
using namespace std;
int main() {
	int x,a,b,c,d,e;
	cin>>x;
	a=x%10;
	b=x/10%10;
	c=x/100%10;
	d=x/1000;
	e=a+b+c+d;
	cout<<e;
		
} 
/**************************************************************
	Problem: 1390
	User: zhuangwenya
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/