#include<bits/stdc++.h>
using namespace std;
int main(){ 
	int a,b,c,d,x,z;
	cin>>x;
	a=x%10;
	b=x/10%10;
	c=x/100%10;
	d=x/1000%10;
	z=a+b+c+d;
	cout<<z;	
}
/**************************************************************
	Problem: 1390
	User: sucongyi
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/