#include using namespace std; #define REP(i, m, n) for (int i = (m); i < (int)(n); i++) #define rep(i, n) REP(i, 0, n) #define rrep(i, x) for (int i = ((int)(x)-1); i >= 0; i--) #define reps(i, n) for (int i = 0; i <= (int)(n); i++) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() #define pb push_back typedef long long ll; typedef pair P; const int inf = INT_MAX; const ll INF = 1LL << 60; const ll mod = 1e9 + 7; int main() { cin.tie(0); ios::sync_with_stdio(false); string s; cin >> s; int n = s.size(); int cnt = 0; vector a; rep(i, n) { if (s[i] == '1') { cnt++; } else if (cnt) { a.pb(cnt); cnt = 0; } } if (cnt) a.pb(cnt); int ans = 0; // rep(i, a.size()) cout << a[i] << ' '; // cout << endl; rep(i, a.size()) { if (a[i] > 2) { ans += 2; } else { ans++; } } cout << ans << endl; return 0; }