#include<bits/stdc++.h>
#define rep(i, n) for (long long i = 0; i < (int)(n); i++)
#define put(i) cout<<fixed<<i<<endl
using namespace std;
using ll = long long;

int main(){
    string c; cin >> c;
    ll ans = 0;

    for(long long i = 1; i < c.size(); i++){
        if(c[i] != '0') ans++;
    }

    put(ans);
}