#include <bits/stdc++.h>

using namespace std;

#define INF 100000000
#define YJ 1145141919
#define INF_INT_MAX 2147483647
#define INF_LL 9223372036854775
#define INF_LL_MAX 9223372036854775807
#define EPS 1e-10
#define MOD 1000000007
#define MOD9 998244353
#define Pi acos(-1)
#define LL long long
#define ULL unsigned long long
#define LD long double

#define int long long

using II = pair<int, int>;

int gcd(int a, int b) { return b != 0 ? gcd(b, a % b) : a; }
int lcm(int a, int b) { return a * b / gcd(a, b); }
int extgcd(int a, int b, int &x, int &y) { int g = a; x = 1; y = 0; if (b != 0) g = extgcd(b, a % b, y, x), y -= (a / b) * x; return g; }

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(a)  begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())

const int MAX_N = 200005;
int N;
string S;

int dp[MAX_N][2];

signed main()
{
  cin >> S; N = S.size();
  reverse(begin(S), end(S));

  REP(n,MAX_N) {
    dp[n][0] = dp[n][1] = INF;
  }

  dp[0][0] = 0;

  REP(n,N) {
    if(S[n] == '0') {
      dp[n+1][0] = min(dp[n+1][0], dp[n][0]);
      
      dp[n+1][0] = min(dp[n+1][0], dp[n][1] + 1);
      dp[n+1][1] = min(dp[n+1][1], dp[n][1] + 1);
    } else {
      dp[n+1][0] = min(dp[n+1][0], dp[n][0]+1);
      dp[n+1][1] = min(dp[n+1][1], dp[n][0]+1);
      
      dp[n+1][1] = min(dp[n+1][1], dp[n][1]);
    }
  }

  cout << min(dp[N][0], dp[N][1]+1) << endl;

  return 0;
}