#include <bits/stdc++.h>
using namespace std;
int main()
{
int n,s,a,b,c,d;
cin>>n;
a=n%10;
b=n/10%10;
c=n/100%10;
d=n/1000;
s=a+b+c+d;
cout<<s;
 
	return 0;
}


/**************************************************************
	Problem: 1390
	User: wqc123
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2072 kb
****************************************************************/