#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,b,c,d,s;
	scanf("%d",&n);
	a=n%10;
	b=n/10%10;
	c=n/100%10;
	d=n/1000%10;
	s=a+b+c+d;
	printf("%d",s);
}
/**************************************************************
	Problem: 1390
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2076 kb
****************************************************************/