#include <bits/stdc++.h>
#define int long long
#define double long double
using namespace std;
const int MOD = 1000000007;
const int INF = 1e14;
using Graph = vector<vector<int>>;

signed main(){
  string S;
  cin >> S;
  int ans = 0;
  for( int i = 0; i < S.size(); i++ ){
    if( S[i] != '0' ) ans++;
  }

  cout << ans-1 << endl;
}