#include<bits/stdc++.h>
using namespace std;
int main(){
	int c,b=0;
	cin>>c;
	while(c!=0){
	    b=b+c%10;
	    c=c/10;
	}
	cout<<b; 
}
/**************************************************************
	Problem: 1119
	User: huanghengyi
	Language: C++
	Result: Accepted
	Time:6 ms
	Memory:2072 kb
****************************************************************/