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

int main(){
    string s; cin >> s;
    int ans = 0;
    rep(i,s.size()){
        if(s[i]!='0') ans++;
    }

    cout << ans - 1 << endl;
}