#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
    cin>>n;
    cout<<n/100+n/10%10+n%10<<endl;
    return 0;
}


/**************************************************************
	Problem: 1027
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/