#include <iostream>
#include <cstring>

char clockwork[100];
int len;

//Legkisebb egyes csoport max legyen
int getFunction_K(int K){
	
	//1. lemásoljuk az arrayt és update k
	char array[100];
	for(int i = 0; i <= len; i++){
		array[i] = clockwork[i];
	}

	for(int i = 0; i < len; i++){
		if(clockwork[i] == '1'){
			array[i+K] = '1';
		}
	}
	
	
	int onemin = 9999;
	int onecounter = 0;
	for(int i = 0; i < len; i++){
		if(array[i] == '1'){
			onecounter++;
		}else{
			if(onecounter < onemin && array[i-1] != '0'){
				onemin = onecounter;
			}
			onecounter = 0;
		}
	}
	
	if(onemin == 9999) {
		return len;
	}
	
	return onemin;
}


int main(){
	scanf("%s",clockwork);
	len = strlen(clockwork);
	
	
	if(clockwork[0] == '0'){ // opti
		printf("-1\n");
		return 0;
	}
	
	
	int itercount = 0;
	while(1){
		//printf("%s jelenlegi\n",clockwork);
		
		int currmax;
		int max = 0;
		int maxk = 0;
		for(int i = 1; i <= len-1; i++){
			currmax = getFunction_K(i);
			if(currmax > max){
				max = currmax;
				maxk = i;
			}
		}
		
		//printf("MaxK = %d\n",maxk);
		

		char copy[len+1];
		
		int countofone = 0;
		
		for(int i = 0; i < len+1;i++){
			copy[i] = clockwork[i];
		}
		
		for(int i = 0; i < len; i++){
			if(copy[i] == '1'){
				clockwork[i+maxk] = '1';
			}
			if(clockwork[i] == '1')countofone++;
		}
		
		if(itercount == 0 && countofone == len && maxk == 0){
			printf("0\n");
			break;
		}
		itercount++;
		
		//printf("countofone: %d\n",countofone);
		if(countofone == len){
			printf("%d\n",itercount);
			break;
		}
	}
	
	
	return 0;
}