#include<bits/stdc++.h>
using namespace std;
int n;
int g,s,b,q;//定义个、十、百、千 
int main(){
   cin>>n;
   g=n%10;
   s=n/10%10;
   b=n/100%10;
   q=n/1000%10;
   cout<<g+s+b+q;
}

/**************************************************************
	Problem: 1390
	User: wangyichen2
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2072 kb
****************************************************************/