#include <bits/stdc++.h>

#define pout(n)  printf ("%d\n", n)

#define rep(i,a,n) for (int i = a;i < n;i++)
#define per(i,n,a) for (int i = n-1;i >= a;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());

const int d4x[4] = {1, 0, -1, 0};
const int d4y[4] = {0, 1, 0, -1};
const int d8x[8] = { 1,1,0,-1,-1,-1,0,1 };
const int d8y[8] = { 0,1,1,1,0,-1,-1,-1 };

#define MAX_N (int)2e5+20
#define INF 1e12+20

typedef long long ll;
using namespace std;
string s;
int ans = 0;
int main() {
    cin >> s;
    rep(i,0,MAX_N){
        int c = s[i];
        if(c != 0){
            ans += c-'0';
        }
        else break;
    }
    pout(ans);
    return 0;
}