#include <iostream>
#include <string>
using namespace std;

int main(){
	string in;
	int i,n;
	int count=0;
	int len;

	cin>>in;

	len=in.length()-1;

	for(i=1;in[i]=='3';i++){
		count++;
	}
	
	if(count==len){
		cout<<count<<endl;
		return 0;
	}

	cout<<"-1"<<endl;
	return 0;
}