#include <stdio.h>

int main() {
	
    int number = 0, resto = 0, sum = 0, new_n = 0;
    scanf("%d", &number);
    
    do {
        resto = number % 10;
        new_n = number / 10;
        number = new_n;
        sum = sum + resto;
    } while (number != 0);
    printf("%d", sum);
    
    
    return 0;
}