#include <iostream>

using namespace std;

int main() {
	string k;
	cin >> k;
	if (k[0] == '0') {
		cout << "-1" << endl;
		return 0;
	}
	
	bool arr[41];
	int arrHelp[41];
	int arrTmp[41];
	for (int i = 0; i < k.length(); i++) {
		arr[i] = arrHelp[i] = (k[i] == '0') ? false : true;	
	}
	int s = k.length();
	bool allOnes = false;
	int cnt = 0;
	int cntMax = 0;
	int tmpCnt = 0;
	int kMax = 0;
	//check full;
	while (true) {
		//for (int i = 0; i < s; ++i) {
		//	cout << arr[i] << " ";
		//}
		//cout << endl;
		cntMax = tmpCnt = kMax = 0;
		allOnes = true;
		for (int i = 0; i < s; ++i) {
			if (!arr[i]) { allOnes = false; break; }
		}
		if (allOnes) { break; }
		cnt++;
		for (int k = 1; k < s; ++k) {
			tmpCnt = 0;
			//for (int j = 0; j < s; ++j) {
			//	arrHelp[j] = arr[j];
			//}
			for (int j = 0; j < s - k; ++j) {
				if (arr[j] == true && arr[j+k] == false) {
					tmpCnt++;
				} 			
			}
			if (tmpCnt > cntMax) { 
				cntMax = tmpCnt;
				kMax = k;
			}
		}

//		cout << "k " << kMax << " " << cntMax << endl;
		for (int i =0; i < s; i++) {
			arrTmp[i] = arr[i];		
		}
		//cout << "-" << endl;
//		for (int i = 0; i < s; ++i) {
//			cout << arr[i] << " ";
//		}
//		cout << endl;
		for (int i = 0; i < s - kMax; ++i) {
			if (arrTmp[i] && !arrTmp[i+kMax]){ 
				arr[i+kMax] = 1;
			}
		}

	//	for (int i = 0; i < s; ++i) {
//			cout << arr[i] << " ";
//		}
 //cout << endl;
	}
	cout << cnt << endl;
	return 0;
}