#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    cout<<n/100+n/10%10+n%10;
}


/**************************************************************
	Problem: 1716
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:27 ms
	Memory:2072 kb
****************************************************************/