#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,x,n;
	cin>>x;
	a=x%10;
	b=x/10%10;
	c=x/100%10;
	d=x/1000;
	n=a+b+c+d;
	cout<<n;
	return 0;
} 
/**************************************************************
	Problem: 1390
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:27 ms
	Memory:2072 kb
****************************************************************/