#include<stdio.h>
void main() 
{
	int i,q,b,s,g;
	scanf("%d",&i);
	q=i/1000;
	b=i/100%10;
	s=i/10%10;
	g=i%10;
	printf("%d",q+b+s+g);
}
/**************************************************************
	Problem: 1390
	User: admin
	Language: C
	Result: Accepted
	Time:21 ms
	Memory:1144 kb
****************************************************************/