include <bits/stdc++.h>

using namespace std;

int main() {

//freopen("test.in","r",stdin);
//freopen("test.out","w,"stdout);
int num;
int sum = 0;

cin >> num;

for (int n = num; n > 0; n /= 10) {
	sum += n % 10;
}

cout << sum << endl;

return 0;

}