#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define COUT(x) cout<<(x)<<"\n"

int main(){
    string s;
    cin >> s;
    int ans = 0;
    REP(i,s.size()){
        ans += (s[i]-48);
    }
    COUT(ans);
}