#include <stdio.h>
 
#define BASE 10
 
int main(void)
{
    int n, digitsum;
 
    scanf("%d", &n);
 
    digitsum = 0;
    while(n) {
        digitsum += n % BASE;
        n /= BASE;
    }
 
    printf("%d\n", digitsum);
 
    return 0;
}










/**************************************************************
	Problem: 1960
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/