#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,h;
	cin>>n;
	h=(n%10)+((n%100)/10)+((n%1000)/100)+(n/1000);
	cout<<h;
	
} 

/**************************************************************
	Problem: 1390
	User: zhengzihao3
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/