#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,c,d,z,m;
	cin>>z;
	a=z%10;
	b=z%100/10;
	c=z%1000/100;
	d=z/1000;
	m=a+b+c+d;
	cout<<m; 
}
/**************************************************************
	Problem: 1390
	User: xuezihong1
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2072 kb
****************************************************************/