#include <stdio.h>

int main() {
    int num, digit1, digit2, digit3, sum;

    scanf("%d", &num);

    digit1 = num / 100;
    digit2 = (num % 100) / 10;
    digit3 = num % 10;

    sum = digit1 + digit2 + digit3;

    printf("%d\n",sum);

    return 0;
}