#include<bits/stdc++.h>
using namespace std;
int main(){
	int i,a=0,b=0,c=0,d=0,h=0;
	cin>>i;
	a=i%10;
	b=i/10%10;
	c=i/100%10;
	d=i/1000;
	h=a+b+c+d;
	cout<<h;
} 
/**************************************************************
	Problem: 1390
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/