#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rrep(i, n) for (int i = 1; i <= n; i++)
ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
ll lcm(ll a, ll b) { return (a * b) / gcd(a,b); }
using P = pair <int, int>;
 
ll MOD = 1000000007;
ll INF =1<<29;

int main() {
     string s;
     cin >>s;
     int ans =0;
     rep(i,s.size()){
         int x = s[i]-'0';
         ans +=x; }
    cout <<ans <<endl;
}