#include <iostream>
#include <string>
using namespace std;

int main()
{
	string s;
	cin >> s;
	int length = s.length();
	int sum = 0, num = 0;

	for (int i = 0;i < length;i++) {
		num = s[i] - 48;
		sum = sum + num;
	}
	cout << sum;
}