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

/**************************************************************
	Problem: 1027
	User: sf751616
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/