#include<stdio.h>
int main()
{
    int num,result=0;
    
    scanf("%d",&num);
    while(num < 0)
        exit(0);
    while(num != 0)
    {
        result += (num%10);
        num = num / 10;
    }
    printf("%d\n",result);
}

/**************************************************************
	Problem: 1119
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/