#include <stdio.h>
#include <stdlib.h>
int main(int argc, const char * argv[]) {

    int n;
    scanf("%d", &n);

    int zbir = 0;
    while(n > 0) {
        int cifra = n % 10;
        zbir += cifra;
        n /= 10;
    }

    printf("%d", zbir);
    return 0;
}