//No.289 数字を全て足そう
#include<iostream>
#include<string>
using namespace std;
int c_to_i(char _c);
int main()
{
	int cnt=0;
	string S;
	cin >> S;
	for (int i = 0; i < S.length(); i++) {
		cnt += c_to_i(S[i]);
	}
	cout << cnt;
	return 0;
}

int c_to_i(char _c)
{
	int nt;

	switch (_c)
	{
		case '1':
			nt = 1;
			break;
		case '2':
			nt = 2;
			break;
		case '3':
			nt = 3;
			break;
		case '4':
			nt = 4;
			break;
		case '5':
			nt = 5;
			break;
		case '6':
			nt = 6;
			break;
		case '7':
			nt = 7;
			break;
		case '8':
			nt = 8;
			break;
		case '9':
			nt = 9;
			break;
		default:
			nt = 0;
			break;
	}
	return nt;
}