#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  string S;
  cin>>S;
  if(S[0] != '1') {
    cout<<-1<<endl;
    return 0;
  }
  if(S.size() == 1){
    cout<<-1<<endl;
    return 0;
  }
  for(int i=1;i<S.size();i++){
    if(S[i] != '3'){
      cout<<-1<<endl;
      return 0;
    }
  }
  cout<<S.size()-1<<endl;
}