#include <iostream>
#include <string>       
using namespace std;//std::を省略

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

	for (int i = 0;i<length;i++) {
		char c = s[i];
		sum = sum + (int)(c - '0');
	}
	cout << sum;
	return 1;
}