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;
}