#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,e;
	cin>>a;
	b=a%10;
	c=a/10%10;
	d=a/100%10;
	e=a/1000;
	b=b+c+d+e;
	cout<<b;
}
/**************************************************************
	Problem: 1390
	User: zengyixuan
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/