#include<bits/stdc++.h>
using namespace std;

typedef long double ld;
typedef long long lli;
typedef pair<int,int> ii;
typedef pair<double,double> dd;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<double> vd;
typedef vector<vector<int>> vvi;

int solve(vector<vector<char>> &dp, int N, int i, int best, int res) {
	cout << dp[res][i] << " " << res << " " << best << " " << i << endl;	
    if (res >= best) return best;
    if (dp[res][i] == '0') return best;
    else {
        int k = 1;
        while(i + k < N && dp[res][i+k] == '1') ++k;
        if (i + k >= N) return res;
		cout << i << " k=" << k << endl;
        for(int K = 1; K <= k; ++K) {
            for(int i = 0; i < N; ++i) dp[res+1][i] = dp[res][i];
            for(int l = 0; l < N; ++l) {
                if (l + K < N && dp[res][l] == '1') dp[res+1][l+K] = '1';
				cout << dp[res+1][l] << endl;
            }
            best = min(best, solve(dp, N, i+k+K-1, best, res+1));
        }
    }
    return best;
}

int solve2(string &S, int N) {
		bool solved = true;
		for(int i = 0; i < S.length(); ++i) if (S[i] == '0') {
				solved = false;
		}
		if (solved) return 0;
		int best = 0, bestk = 0;
		for(int k = 1; k < N; ++k) {
				int c = 0;
				for(int l = 0; l < S.length(); ++l) {
						if (S[l] == '1' && l + k < N)
								if (S[l+k] == '0') {
										c++;
								}
				}
				if (c > best) {
						bestk = k; best = c;
				}
		}
		//cout << bestk << endl;
		string S2(S);
		for(int l = 0; l < S.length(); ++l) {
				if (S[l] == '1' && l + bestk < N)
				S2[l + bestk] = '1';
				
		}
		return 1 + solve2(S2, N);
}


int main(int argc, char** argv) {
    ios::sync_with_stdio(false);
    string S; cin >> S;
//    vector<vector<char>> dp(50, vector<char>(50));
//    for(int i = 0; i < S.length(); ++i) dp[0][i] = S[i];
//    int res =  solve(dp, S.length(), 0, 1000, 0);
//    if (res == 1000) cout << -1 << endl;
//    else cout << res << endl;
	if (S[0] == '0') {
		cout << -1 << endl;
	} else {
		cout << solve2(S, S.length()) << endl;
	}
    return 0;
}