#include<bits/stdc++.h>
using namespace std;
int main(){
	int x,i=0,a=0,s=0,o=0,z=0;
	cin>>x;
		i=x%10;
		a=x%100/10;
		s=x%1000/100;
		z=i+a+s;
		cout<<z;
    }

/**************************************************************
	Problem: 1027
	User: huxuanchen
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/