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

int main(){
  string S;
  cin>>S;
  if(S.at(0) != '1'){
    cout<<-1<<endl;
    return 0;
  }
  for(int i=1;i<S.length();i++){
    if(S.at(i) != '3'){
      cout<<-1<<endl;
      return 0;
    }
  }
  if(S.length()==1){
    cout<<-1<<endl;
    return 0;
  }
  cout<<S.length()-1<<endl;
  
  return 0;
}