#include <cstdio>

int main() {
    int n;
    scanf("%d", &n);
    
    int sum = 0;
    while (n > 0) {
        sum += n % 10;
        n /= 10;
    }
    
    printf("%d\n", sum);
    return 0;
}
/**************************************************************
	Problem: 1418
	User: huangcanwu
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:1144 kb
****************************************************************/